Under Gravel Filters SUCK! Why Grandpa's old aquarium filter is a thing of the past 

Grandpa here, used them for over 30 years on multiple tanks with great success. Wish I never changed to canister filters.

I still use UGFs on most of my tanks and I have never regretted using it.

For everyone thining UGF do a bad job, are inefficient and do a worse job than another filter, save a landfill and ship those old (even broken) UGF to me. In my experience the issues people claim to have from UFGs is from lack of knowledge of how to properly use them, repeating misinformation they have heard, and the negative PR campaigns the manufactuers did begining in 1976 in order to boost sales of their newly released hang on back power filters. I have multiple tanks running UGF from cichlids to planted tanks and havent had near as many problems as i have with other filtration types. Its all about knowing what you are doing and using it properly. Here are 10 common misinformations that gets spread 1. The debris under the plate is harmful 2. You have to clean under the plate 3. You need heavy air flow to make it work 4. You cannot add on anything else to help if needed 5. You cant use live plants with UGF 6. You should deeply gravel vac all the gravel 7. You need the uplift tubes to the top of the tank 8. You can put a powerhead on just one of the uplift tubes to help 9. UGF can only do 1 kind of filtration 10. A broken UGF will not operate properly

I have switched to using an UGF. No looking back. The slower you run them, the better they work.

Respectfully, I think you couldn't be more wrong. UGF's are so easy to use. I combine mine with a HOB filter. I find it to be much better looking in my tank. The combination of these two filters do a great job. I feel that sponge filters are the ugliest thing you could put in your tank. Who wants a dirty sponge sitting in the corner of your tank? The longer you have an UGF, the better it works.

I've been using them for a couple years now and my plants roots are so much healthier looking now because they are no longer in an Anaerobic environment

I run a UGF along with a Tidal 55 been running it for 3 years with absolutely no issues in my 38 gallon tank.

I have an old Aquarium Fish Hobbyist magazine and there was an article where they hooked up the up tube of the UGF to a HOB and the HOB pump drove the UGF. Pretty creative for 1970’s

I have been using an UGF for 1 yr, 4 months and 30 days. Zero Ammonia, zero nitrite and zero nitrate. It took awhile for the beneficial bacteria to colonize during the fluctuations of the nitrate levels but now the tank is pretty well balanced. Five guppies, one snail, two Borneo Loaches and a decent size Ranchu Goldfish all live in a 20 gallon tank together. The UGF that I use is the same UGF that was in this video. The UGF worked for my 20 gallon for several months and I’m excited to work on my next project using an UGF. This is such a rewarding hobby when our pets thrive in a safe and healthy environment.

I used UGF in my 4 3-foot tanks fitted with power heads instead of air stones. They ran great and regularly had a lot of baby fish swimming about. I just did a quick weekly turn over with a siphon gravel cleaner alongside partial water changes. The catfish loved rooting around in the pea gravel too. If I get more fish tanks again in future. I will be using UGF again. The other bonus to UGF is that you don't have to buy replacement filter media every few months. I guess that is why shops try to push people in that direction (£$£$£$£ recurring sales against one off UGF sale)

Hi, I don't understand, I just finished watching your video claiming how great the UGFs are. Which is it, is it great or does it suck?

I’ve used several UGF’s and never had an issue. My gravel was not too deep and they always seemed to work great once the cycle was established. Interestingly, as a teacher I set up a tank to hatch trout eggs through a program called FinS and they had fairy tight parameters on how they wanted the tank set up. Yup, they required an UGF with a powerhead on one uplift tube and a canister filter pulling water through the other uplift tube, as well as a chiller of course. Worked well!

Back when I first kept fish in the 90s, I used under gravel filters without issues, however I didn't use air stone and pumps. To run a 55G for example, I had a power head on top of the tube at each back corner and a very small HOB in the middle for more flow. I used a very fine gravel (slightly coarser than coarse sand) and what I found was that with the power heads the only place where the mulm actually built up was along the front 3rd area of the tank (under the gravel). A couple of times a year I simply shifted the gravel to the back 2/3 and used a python (a new-fangled gadget in those days) to suck the muck up through the exposed vents in the filter plates, then did a bit of rescaping. Not that hard, really. No "deep" gravel bed... not really needed... besides, how does the surface area of a shallow bed (say 1" or so) compare to the surface area of a couple of average sponge filters in each corner? The difference is negligible. I wouldn't recommend running right out to buy one, but I would say they belong in that gray area between rock and suck! lol

I had to double-check the date this video is uploaded to make sure it wasn't on April Fools day

Can't wait to hear next week's video. Currently, I am experimenting with a slow moving plenum and a canister filter. The slow moving plenum is a different concept than the modern ugf. The ugf tries to suck as much water through the substrate as possible to use the gravel as a mechanical filter. This creates more aerobic environment in the substrate which as you said creates nitrates (but so does canister filters, sponge filters, etc). In the slow moving plenum the idea is to slow the water movement down so that at a certain depth we achieve a low oxygen environment (anoxic), but not anaerobic (no oxygen). The anoxic environment is where a certain type of bacteria can thrive and it converts nitrates into nitrogen. To help this bacteria get started we can use a clay source of substrate like certain types of clay kitty litter, etc, along with an iron source which helps the growth of this bacteria. Check out Kevin Novak's videos on this subject. One test to see if this is working is to check if your nitrates are low (

I have used those since the 90s and when I got back into the hobby started one in my 55 never regretted it one of the best filters ever with power heads

I totally disagree that ugf's are not good filters. I used them for years on both fresh and salt water without any problems. I also never had an issue cleaning underneath them, it was simple to siphon the muck out by sticking a hose down one of the tubes. These days I use sand because I prefer that look so the ugf is out. Just remember that just because we have new tech out these days, the old ways worked for many years without issue. ** On a side note, I think I have to clean my Oscar tank more often now with sand and 2 FX 6's than I did with an UGF and 4 powerheads.

Hi Bentley. I used an UGF for many years without any problems before moving to powerheads & canisters and have now gone back to using UGFs to create a plenum for an anoxic filter. In my experience it took my anoxic filter about 8 months to break in and I now have zero nitrates. I still do occassional water changes to replace minerals & top up evaporation. In an anoxic system you don't need a very strong flow through it. You actually need a very slow flow in order to create the anoxic conditions so either reducing the air flow or shortening the uplift tube works fine. Also what I found is the mulm once broken down is inert so does not produce any nitrates. I don't have any plants in my tanks as the goldfish decimate them in no time. Excellent and interesting video. I cant wait to see the pros after watching so many negatives about UGFs. 😀🙏👍

Hey Bentley I have 35 aquariums and everyone of them has a ugf in them running them as slow moving plenum I have had great success doing things this way I always have very low nitrates and phosphate my tanks are always heavily stocked every tank gets a 50% water change not for nitrate removal but to re mineralise and the plants like the fresh water I will never setup a new aquarium without first putting down a under gravel filter it allows the movement of water through the substrate thus avoiding anaerobic bacteria and hydrogen sulphide gasses it also helps draw nutrients into the substrate for plants to uptake and if used correctly you do not end up clogged up by mulm and detritus you need to move water very slowly through them to achieve anoxic conditions that I have found to work perfectly

I understand, but then why did it work for us for years? In the early 1960s. We had a 20 gallon overstocked live breeder tank. Just had chlorine in the water, so let new water sit overnight, no need for dechlorinator as we didn’t have chloramine. Gravel was about 1 inch thick. We never tore it down. Gravel vacuumed rarely. We did have a kuliloach that lived most of the time in the gravel and would eat the gunk. No, I am not going back to a UGF, but still, why did it work so well. And our water was clear. And, we did a water change, (about 20 percent) about once a month.

Why does one need/want to clean under the undergravel filter? The bacterial culture under the plates should be left not disturbed for many years Slow sand and fast filters are used to produce very clean potable water. UGF filters rock

I have an undergravel filter on a 29 gallon aquarium that I've had running since I was teenager in the 70's. I have more tanks that i've set up more recently, and use either canister filters or sponge filters. I totally agree with the aggravation of the cleaning, which I used to do once a year but now every 2-3 years. And I've got live plants, which means basicallly re-aquascaping when I do clean it. But my parameters stay pretty steady, and it is lower maintenance on a monthly basis than the canisters and sponge filters. I like the benefits of all of them, in the right situation.

Another Grandpa here. Sorry, but WOW! Everything you said is wrong. I've run UGF for 40 years. I've tried HOB's and canisters and I find them inferior and expensive. UGF are cheap, easy to maintain, no expensive media to buy every month, they just work and they work great! And they're less hassle to maintain.

Sorry, but I beg to differ. I ran a Penn-Plax Undertow in my 55g for three decades (70's to 90's) with no problems, it was very sturdy. One thing the old gentleman who owned the LFS recommended I do was to place garden weed cloth on top of the plant. My gravel was 3 to 4 mm in size. It was 1 1/2 to 2 inches in the front, 2 1/2 to 3 inches in the back. I had just a few real plants including a few Amazon Swords. While doing my weekly water change, I would gravel vac half the tank: The following week the other half. The nitrates stayed below 20 ppm. When I broke the tank down in the 90's to move there was no large accumulation of milk under the plate.

Bentley, I normally agree with your opinion on these type of things but in this case...not. I completely disagree with your points and have over 40 years of experience with UGF's. They work fantastic for the vast majority of set ups. Obviously your not going to use one in a tank with fine sand...but coarse sand up to "standard" gravel is fine. And of course a dirted tank with a UGF would be silly. They work great for unplanted and planted tanks alike. The cleaning interval is not measured in weeks or months. It is measured in years...if ever. The uplift tube is no uglier than a sponge filter. A tank with a UGF can absolutely be gently gravel vac'ed with no issues. They are literally a life insurance policy for your aquarium. When the HOB dies, no need to panic...the UGF will keep things going until you get a replacement. Same for a canister. Lose your cycle for some reason? Usually NOT if you have a UGF. Put it in when you set up your tank and forget it's there. It will be a hot bed of bacteria to save you when you mess up. And they do NOT need a high flow rate. Just enough to get a little flow through the uplift tube. And these days you wouldn't run just a UGF. You would use it as a bio filter only. And FWIW the example you chose to display is garbage. Much better units have existed for decades. Your comments on Nitrates are not true either in my experience. I have heard all of your arguments for years. 99% from people that have never actually tested or even used UGF's. And I think that's the case here as well. I think this video is a rather obvious "click generator" and your info is so bad it will probably be a home run for you. I certainly felt the need to comment...LOL!

I did a under gravel filter in combo with an HOB on a 20 gallon and it worked out well . I did have some plants and the large tetra air pump. I didn't even know about some options of filtration back in those days.

Ran my 150 gallon Salt water tank you years with a “ REVERSE “ flow under gravel filter. Used a large canister and ran it down the tube with clean and oxygenated water up thru the gravel. Never had a problem.

I have just the one UGF. I wouldn’t mind having a few more of them for a couple of my other tanks. Can’t use them with sand, so they’re not suitable for all my tanks, but on gravel it works brilliant.

I have a 20 gallon tank with 2 UGF and a canister filter rated for for a 15 gallon tank and they work great. The charcoal canisters make my water clear and the ugf keeps my plant roots perfectly oxygenated.

i used that thing during the 90's with my first tank with pebbles with no plants, its easy to clean, lol.

One of the 1st filters I ever used came with a hexagon 5 or 10 gallon tank I had as a child (showing my age here im a 45 year old grandma and This was in the 80's). I really wish Tetra still sold that kit!. The second filter I had was a box filter and MAN ! That thing was a pain in the rump! 🫣 If you could keep it submerged was 1 of the biggest complaints but man was that messy!

Mine works too well. I keep up with my weekly maintenance and so far so good. I dont run a natural tank with sand as its a whole other category of setup but for what it cost. Its brilliant. Im 35 and yet to be a grandpa but i do see where the boomers are coming from with their support for UGF

I have an undergravel filter in my current tank. In addition, I have a 2 way gang valve and an old air-driven Lee's Quick & Easy filter in the opposite corner. These have been discontinued and once my current supply of cartiges is gone I will cut floss pad to fit and use it mostly for mechancal filtration as a box filter. I've always used air driven filters, and I think it goes back to my grandma and her guppy tanks. She may well have kept them to provide idle grandkids a chore, but we learned a lot about fishkeeping...in the 1970s. Now, if you'll excuse me, I gotta go outside and yell at kids to get off the lawn. 😆

I used an undergravel filter in the 60s. There was no plate, just a network of tubes with holes for the air and water to circulate through. But that was before water changes and gravel vac were just coming about and that was thr only reason we did water changes. The only plants available were eloda and cabomba and plant fertilizer was recommended at 1 capful a month. Then i went to box filters. I liked those alot. What do you think of those. They are hard to find now with all the pushing of sponge filters which with my OCD, I can't stand seeing all that gunk falling back inti the water. Getting a bag aroung the sponge is impossible with my 70 year old fingers and not nearly long enough arms unless the tank was on the floor, maybe?

Have you ever used one? Which filter doesn’t have a tube going up or down?

I used to use an undergravel filter with an aquarium I had as a kid. It seemed to do a good job. I just would use a siphon vacuum to clean the gravel every so often. I never thought that they were bad. I would still use one if I got a new aquarium. I also don't like the outside cartridge filters that hang off the back of an aquarium. The filter that is used n a nephew's aquarium just gets dirty too fast. They may be charcoal, but they are more maintenance if they filters are not replace regularly. That's my two cents.

I really like running anoxic filtration when done right. I run most of my tanks in this way or bcb canisters. When setup right, you can control how much nutrients get into your substrate by dosing the water alone if done with kitty litter. Since the flow is so slow and the binding nature of kitty litter the plants benefit greatly. Fairly cost effective way to filter a tank since, if done right, can reduce nitrates and reduce the need for large water changes. Just my two cents

I've been using an UGF for almost two years in my planted tank 0 issues whatsoever, I came across the plenum concept and I've been putting it to the test, and so far I am completely pleased, the bottom is still clear after about teo years, I only use it as a biological filtration, my mechanical filtration is in charge of a canister filter, I love how the filters combination has been working so far, I personally won't stop using them and I will continue to recommend their use, they are definitely not necessary to have a successful tank, however they do a good job in helping keeping things alive, there's proof everywhere showing that they di in fact work pretty well. 🙂

Help! The risers are too long, how can I cut them? I have a Penn Plax in a 20 Gallon Long.

i really want to try a diy version with pvc pipes wrapped in 35 micron nylon mesh and german jetlifters. would injecting co2 through that system make the plants go wild? god i wish i had money to find out

Bentley, you're clearly not an idiot but you're wrong. Sponge filters are for unimaginative aquarist. Many of us have used reverse flow undergravel systems for years. Use them with either cannister or an internal pump. Could be used with a HOB. There's so many ways to use them and you make some excellent points, if used wrong there could be devastating results but most who go down the UGF route, do so with a great deal of research, trail and error and experimentation. That's what the hobby is about. Almost always, the answer is, keep it simple and let nature do it's thing.

The UGF is GREAT for planted tanks but Ive always used them with canister filters. The plants LOVE it

props for even being able to find one for the video, lol!

Your right about everything you said, except that you don't have new ideas to improve the outdated idea, I have improved it and I don't need to vacuum the gravel .

I love undergravel filter, I made my own, and connected a strong hangover filter on one side of the tank, and on the other side a water transfer pump to do water changes and it cleans all of the bottom settlement of food & poop that causes viruses & sickness, my hangover filter saves the good bacteria & my water transfer pump cleans the bad bacteria of food & poop from the bottom of the gravel.

I actually still have two in use in a 10-gallon and 30-gallon. It's mostly used for surface aeration along with some sponge filters. My water is clear and lots of air is moving along the surface... and my fish are Happy! The tubes are clear, so what do you mean "ugly"? You should always be maintaining your tank, anyway. It's not as much of a hassle as you seem to making it out to be.

I have had tanks set up for 20 years with no problems and I always ran one of my canisters down the tube so never collected under. Also gravel was always 2 to 3 inches deep and had cut down plastic jugs for planted area with just a few slits in bottom. This way only broke down tank if had to move it for new carpet or floor. Like I said love them.

used UGF years ago and recently got back into the hobby. 40 Gallon breeder tank set up with live plants and UGF. Set up for two years now and it runs beautifully with next to zero maintenance! Lots of fish and no maintenance for a minimal cost. So tell me again why they suck???

Keep up to date Benley you don't use air anymore you use a powerhead which make the system much more efficient

I have had a 125-gallon tank with an under-gravel filter for nearly 10 years. I did modify it a little. In order to use Lesley pool filter sand, I glued nylon fabric to it so the sand doesn't not go through it. I Am also using 4 powers heads to run it. I vacuum the sand every month or so to allow water to flow through it well. My clown loaches don't allow me to keep Malaysian trumpet snails. If I don't vacuum the sand, I find that it gets compacted with fine organic matter which may not let water to flow through it as well as it should. Mulm builds up below the plate. You will never see it until you brake the tank down. You don't have to do anything to get rid of the mulm, It does not cause nitrogen problems. It probably becomes inert carbon after all the microbes have gotten to it.

I use under gravel with my canister filter. Been doing it that way for years. I don't have to do complete water changes anymore. Under gravel is the way to go

Not the subject of the video, but I really like the scape in the aquarium over your right shoulder.

One major advantage of an UGF is in case of a blackout. Just throw on a battery powered air pump and you're all good

I have a python gravel cleaner that sucks all that gunk out that settles under the filter

This Grandpa loves UGF's.

This guy has no idea what he is talking about, top level comedy!

Underground gravel filters are the best biological filtration in the hobby I always have a ton of success with them and they're great to combine with a lot of other filters

Sorry, I really liked lots of your other videos, but on this one I feel it isn't as complete and accurate as it could be. On the potential issue with air bubbler and water level, I think this can be mitigated by driving the UGF with a small powerhead. Also, I believe UGF can function well with 2-3in of gravel, which isn't all that different than typical substrate thickness. In any case, keep your good work, always interesting to watch your videos!

Interesting downsides- I think the amount of flow you put through an UGF probably has a lot to do with the amount & type of servicing required? Is it not just common sense that easy servicing of UGF would be by inserting a hose down the airlift tube to syphone any debris from under the plates out that way? Surly people don't strip the substrate down since that is the major source of mechanical & biological filtration for the tank? Do agree that some people think UGF is something it inherently isnt, but that is also true of other types of filtration, so IMO, that is more of a people problem not an UGF/any one type of filtration problem. For me the downside for UGF is one of the downsides of sponge filtration- the bubbling nosie, thankfully it can be mitigated to a large extent by experimenting with different airstones, but if you don't like the sound of bubbling water, airdriven UGFs are not the way to go :p Also not sure if an UGF would be my first choice or even a good chocie for say an African cichlid setup, so I guess another downside might be some limits on the types of fish that can be kept with UGF? IME, slow flow UGFs rock & are low maintenance, high value for my soft water breeding set ups. Mine have mixed types & sizes of substrates (kitty litter or crushed volcanic rock & baked clay under sand caps thant range from fine to coarse ), which varies from 8cm to 15cm deep & they don't have any build-up under the plates (yet) after a couple of years running. All mine are setup for wild betta & parosphromenus tho, so more nano-type fish than anything & while I do have to feed heavily, I find the water quality stays stable & near perfect for the species I keep (if I skimped on water changes for more than a month I'd run into a TDS issues I think hence the "near" perfect), which it has to be in order to get breeding that results in viable eggs & fry for some of the species.

I was wearing that same hat while watching this video haha. Go Topes!

I just wanted to mention that the Lee's UGF is much sturdier than the Penn-Plax one.

Great video topic. What’s your thoughts on planted tanks with UGF. Can it hurt plant growth. It seems like it did for me. But I’m not sure if it was the UGF of some other issue.

The under gravel filter is like any system. You need to know what you're doing. One place drilled a hole in the bottom of their tanks so you opened it and the mulm came out. Quite clever. 🙂

I literally just watched a video by you talking about why they were the best??? You were talking about using them with a power head and putting media under a UGF when you use it.

Funny thing is I recently had to split up my two Oscars and their tank mates. (Was meant to be a pair but the girl turned out not so Girly 😅) For a short time as I was considering how I was going to achieve this I briefly considered under-gravel set up for them vs HOB or Sponge because they would be downgrading from a shared 120 to separate 55's. Main reason for my waffling was space, noise and maintenance, with a HOB they can get a bit noisy at times and also have a bit of a real Maintenace schedule to keep it effective. With a Sponge you now have one or two chunky items in the tank where space is at a minimum with this downgrade. Now an under-gavel setup the 2-4 uplift tubes are the only contention for space. Ultimately, I settled on sponge because I already had a few seeded and ready to go. To answer your simple question at the end of the video: Yes, I have used these many times in a wide range of tank sizes, but the best was 2 examples. Both being breeding setups #1 Bristle nose, a 10 gallon with only half coverage and a fairly thin layer of gravel but piled high near the uplift tube this would provide a good circular flow in the tank. #2 Convicts, this one is an odd one it's in a 55 with full coverage but only one functioning uplift tube in the corner but 3 more uplift tube bases installed without air and about 2" of gavel, this gave the fry complete ability to hide from the parents if they ever felt the need to eat them. This wasn't needed for the first set of fry but after amassing older siblings in the tank the parents would occasionally eat the current fry and start over. Now adays nobody keeps convicts but I to this day consider them my favorite cichlid species.

Mulm should not get under gravel. If it does you don't have enough or the right sizes of gravel.

I don't agree. At all. UGF are amazing

I use an ugf and a hang on the back. Always did, always will.

Can't wait to watch this one after chores and to-do list today. As a diehard UGF fan, I may have to send you a poo poo emoji to hold over till next video explaining why they rock! Hahaha. Be back soon my friend

Respectfully, you're actually not meant to service them at all ever. Use 2 to 6mm gravel. You're not meant to clean them. The gunk is meant to be left alone. And for the love of god, do not gravel vacuum these! And no nitrates will not stay elevated. An improvement is to add a power head on top. So yeah, they don't suck. Also, sponge filter uplift tubes are meant to be taller to give better pull.

Im just over a year into this lifestyle. Ive bought internal filters for my five tanks. Already had two filters break. Im now changing to undergravel filters. Ive changed one over, already water is crystal clear, plants are doing great. Ill be changing the rest of my tanks over

I have a ugf on my 75 gal & I like it, but I have powerhead pumps not air I got sick a month later after I had set it up, spent 6 mons in the hosp husband just fed the fish while I was laid up in the hosp, he didn't do any water changes just top offs, the power pumps got clog at some point & I didn't know till I could get out of the hosp 6 mons later. hum When I did see my tank I was in awe at what I seen, there was slimy algae & hair algae the tank no water movement it was a Mess : > ( 3 mons later since I've been home I made some great improvements. 1 on my health, working on the tank every chance I could instead of laying or sitting in front of the tv all day recovering to get my strength back I worked as much as I could on it & it's just as clear as ever. But you are right about the down falls of how it works which isn't a bad thing if people like it, but I'm going to take mine out & change it up with 2 internal pumps & rescape it with what plants I have that's grown into the plates : > { which isn't never good, so that's my 10 cents ha ha ha

Switching away from undergravel filters was one of the worst things I have done... in the hobby. Back in the day UG filters were not flimsy. They were made primarily by a company called Penn-Plax and were a hard zig zaggy plastic with grooves and stuff and they were sturdy enough that you could jump on top of them. New generation of UG filters are flimsy... but then again we kinda sort of moved away from UG in the first place as a hobby. Introduction of powerheads (walmart sells them still to this day) when connected to the UG filter made them work like a machine. Unfortunately as you said... you had to rip everything out to service the darn thing. That made a giant mess etc etc. And so... there are 2 ways to make "that" process easy peasy lemon squeazy. #1 Buy super big diameter hose (like 3/4 inch, 1 inch diameter) about 6-10 feet long and put a bucket inside of a plastic container. Suck it all out so it collects into a bucket and water runs over into container and you can have a pump to pump it all out while you are doing it. Honestly you don't have to do all that assuming you gravel vaccing the bejesus out of it at least once a month. #2 If you have a drilled aquarium you have struck a motherload (more specifically if its drilled in center or both sides). You would not be running it as a overflow setup but rather using drilled bulkhead setup to have a valve on bottom of your tank with hose connected and once a year basically open the valve and get all that gunk drain out into flower bed or something. I learned it from a guy in 1999 who got me into fish hobby. He had a 250 gal tank with UG, drilled and a long hose coming out to outside. I learned everything about the hobby because I cleaned his tank every week. My first tank was a 20 long with UG setup which I ran as a gravel filter of choice (tried HOBs) 1999-2009 and stupid me had to go and switch to a fluval canister filter 405... that constantly leaked... switched to HOBs etc etc... then eventually in 2014 I switched to fluidized K1 for my 300 gal and now with a 3 barrel K1 method but all my planted tanks run on fx6s which I hate with dire passion. As for UG filters... there are actually 2 ways to run them. #1 Traditionally where it "sucks" #2 In reverse. Running it in reverse means water travels down the tube under the filter and through the gravel and out into tank. Doing that captures all the gunk under the plates and that is where drilled aquarium would work amazing to flush it or you can disconnect reverse pump and suck it all back out via tube to flower bed without really disassembling the tank. I would obviously not recommend to use UG filter for planted tanks... because it adds a whole new level of complexity.

I'm confused, u have another video on these being the best ugf. So which is it do they suck or not?

Years ago I used a under gravel filer. And to clean out the void under it. I would move a power head from uplift tube to uplift tube. And then do a large water change. It was very effective. You could watch the waste being sucked towards the tubes from under the tank. And back then it allowed me to tie my fake plants to to the filter. To prevent my Oscars from rearranging them lol! But since iv moved on to live plants and community fish I couldn't imagine going back to an under gravel filter.

I do agree that the old way of using UGF do suck. Using a air stone or power head just does not work well. you also need to have root plants other wise then yes all that stuff under the filter needs to be removed.

GOOD EXPLANATION :) THANK YOU FOR SHARING :) THANK YOU FROM ISRAEL :)

Hello Bentley,,I never had to remove it the plate because I would stick my siphon hole down the tube and out came the muck,Also I use power head on the pipes on the top ,and yes your right the news are made cheap, if you look up the the vintage under filter,,it was built with less slot on the plate ,you fan mg, see you on the next video, ps,siphon was done ever 6month,

UGF has one serious problem. How to make sure that the roots of plants do not grow through the holes of UGF?

Interesting. I used them back in the day…without plants…to great success. Now plants. Experimenting with dirted. Ergo, not on my list right now

Do your homework. You are dead wrong. I have been keeping fish for 67 years and I've used undergravel filters the whole time. I have absolutely nothing negative to say about the UG filters.

Please do the entire aquarium community a favor and do a deep dive into nitrates- how much is too much? Papers that show that growth is decreased and mortality is increased at a particular point? Aquaculture/ public aquariums attitude towards nitrate? Level of nitrate vs turbidity produced by food/poop breakdown with increased free floating bacteria? Any any more questions that need answering. Not opinion, not expert opinions, but papers that seem to answer these questions and perhaps aquaculture people opinions This will hopefully put to rest the ongoing raging debates on these topics.

If you slow down the water flow you created an onoxic filtration

So... What should we do??? 😅

I left a comment that I thought you were "spot on" with regards to UG filters. It was removed. Why?

Please let me know if, perhaps sticking a rooted stem of pothos down under there when setting one up might be a good idea?

Bently, I love all your videos, but today I TOTALLY DISAGREE!!! I am a 50 year freshwater & plant expert, and ALL my heavly planted 35+ tanks run with under gravel filters. There are numerous ways to use UGF, by themselves, or in conjunction with HOB or canister filters... The things that you said were as issues, ARE NOT, and i'd be willing to talk on your channel to show why... I still love you, but here, YOU'RE WRONG...

Surprised to see this from @bentley Pascoe lots lots of misinformation here. They can work and work well with none of the issues mentioned, which are either not true, easily solved, and contradictory. Uggh.

A bit confused - I watched "Scretly the best" now this - Hard to turst your advice - LOL

I'm confused, haven't I just seen a video from you saying how great UGFs are? 🤷🏻‍♂️

what company do you work for? New tech?

I could ride around town on a horse, but I rather ride in a car. Same thing applies to an UG filter vs a canister filter. Case closed!

Works well as a planum though.

6:53 i agree that the plates are flimsy and easily broken. Wish the spacing would be more too. Would like them to be an inch tall. Noticed the affliated link for a ugf. Of people want to try it, they need to know where to get it 😊

Slow moving plenum n u can always siphon the gravel

I like how this dude baited everyone with why these SUCK, and also has a video on how their the best ever ha..

What if I attach it to a canister filter hehehe that’s what I’m about to do for my 300 gal tank

Yet another video with nothing but misinformation

Huh. Looking forward to the follow-up video... 😐

I use to have one of them like 20 years ago 😂😂😂😂😂