Fish Tank Water Hardness Fully Explained: Don't Kill Your Fish! 

Hey Everyone. If you are interested in testing your water here are the links to testing strips/kits! Amazon Affiliate Links: Tetra Water Test Strips: amzn.to/2E94zC9 API 5 in 1 Water Test Strips: amzn.to/2EeHIoK API Ammonia Test Strips: amzn.to/2XvghA6 Apera pH meter: amzn.to/2NryycT

this feels like a science class

I'm an engineer by profession, and I can tell you, this was beautifully explained! All my respects for you and your passion.

I had to learn this lesson the hard way when I recently got back into the hobby after a 20 year (or so) absence. My PH coming out of my tap was around 7.5 give or take, but I noticed that every time that I tested my tank when trying to cycle it, the PH would drop down to 6.0 or lower....Which in turn killed the cycle. I was trying to cycle a somewhat heavily planted tank that had a PH lowering substrate and driftwood which would have been fine, but I figured out that my tap water's KH was extremely low with no buffering capacity. It was a nightmare trying to cycle this tank before I figured everything out with a ton of research and some crushed coral. I wish that I would have come across this video sooner, because it would have saved me a bunch of time and work. With that being said, this video is awesome! Thank you for all of the informative and entertaining content! Hope to catch a live stream sometime soon and become a member!

When I REALLY need info I come to Jason. Thank you for all the education for someone who's been out of the hobby for 40 years. Lot's have changed.

I watched the PH first and now the water harness. You totally told me the opposite my local fist store told me. I told them my PH is at 8.3. Out of my tap it is 8.5. My GH/KH is at 20 ppm - 30 ppm. My local fist store told me I need to drop my PH and told me to put the leaves in my tank. With your explanation I now understand how harmful it would be to do a drastic change. You made it quit clear to me that I am ok, but should balance it out slowly. It is important to to balance the PH to maintain it between 6 - 8 and monitor my hardness to keep in line with the PH. Sorry to repeat. Thank you for sharing.

I love these educational videos!! I watched this one the other day and had to come back again today to watch it again to make sure I soaked it all in. I understood the basics of hardness and that kh points to buffering capacity but this is some great in-depth info!

I can always count on The Professor with any test tube questions. Appreciate you Jason

Your videos are super helpful and informative...thank you. I'm new to fishkeeping and the amount of information I really needed to know BEFORE, is overwhelming. Thanks for providing this content. It's appreciated!

Love the video. Most important point was to keep the PH stable and thanks for speaking about water buffering capacity too that was important piece to understand, thanks for these refreshing videos.

Another excellent vid mate. That is one of the best youtube breakdowns of water hardness I have seen. You are quickly becoming one of my fish youtubers. The fact that you refer to your tanks as an ecosystem might be missed by many, but essentially this is what we do as fishkeepers. We attempt to create ecosystems that emulate the natural ecosystems. Of course you can never achieve a fully natural ecosystem for tropical fish in non-tropical areas, some artificial input is required, but I have found in 22 years in the hobby that the closer you get, the more success you will have with your fish. My tip to all would be not to chase your water.....essentially work out what your water parameters are, then choose the fish you stock based on those parameters. Keep in mind that many commonly kept aquarium fish will thrive in water conditions drastically different to those of their natural habitats. Evolution happens fairly quickly in organisms with a short reproductive cycle, and many species have been successfully bred for so long in the hobby that their tolerances are actually quite extreme. For example, I probably wouldn't keep wild caught Rift Lake Cichlids in my water, as although it is relatively hard, it has a pH of around 7.3, but the fish I have stocked are bred in the local area and are absolutely thriving. They have never known anything but a pH of 7.3. I also know of people who breed Discus in this water successfully, and I would quite happily keep those Discus in this water as well, although it would likely kill a wild caught specimen. Aim for stability folks....fish thrive in a stable environment.

So great that give the actual science of water parameters and not just the opinions. Very helpful.

Extremely effective explanation! I live in the same area as you just down in Indiana. Very hard water with a high pH. Finally decided that I wanted to separate tank where the fish will thrive in my natural water parameters. Siding on going with a large frontosa colony! Thank you for your help!

I just found this video, it is really awesome. Thanks for breaking the subject down it made perfect sense and really helps me for when I'm finally able to shop for my fish and shrimp.😁

Absolutely love your videos. Very helpful and educational. You do an absolutely fantabulous job of teaching. Keep up your total awesomeness.

You're so good at explaining this stuff! I really appreciate it. Your channel is my go-to source for all the newbie stuff I need to know. Thanks so much!

Thank you Jason! Awsome channel! Always well explained!

Great video! I appreciate your depth of knowledge and energy. Answered all of my questions on maintaining a healthy tank.

Thanks so much! This was very informative.

Extremely informative! Thank you!

Hi Jason fantastic presentation time well spent, aside from buying stuff this may be my favorite part of this hobby... thanks

This is what I needed explaining correctly, great educational video, thank you prime time. 👌👍💚

Thank you for all this informations!

I love stuff like this. I would love to see a long video where you really get into the weeds talking about these things. It's been a long time since I took college chemistry after all. :)

Wow this is great information for a more intermediate keeper like myself. This improved my understanding quite a bit.

This could not have been any more helpful!! You explained this in such an easily digestible way, thank you! I recently moved to downtown Chicago and the lifespan of my fish had drastically decreased, and they never seemed to thrive like they used to. Now I suppose I know why. Time to look at hard water fish species! Thanks again!

Wow, awesome breakdown, very in depth on how each parameter influences the others....can see why keeping things stable can be more important then a one parameter goal like PH level or Total Alkalinity.

Thanks for the video. I have returned to fish keeping after a long break and I now live in virginia. I have almost zero kh and dh. The ph out of the tap is 7.2, but after sitting for a few days drops to 6.2. At night my CO2 in my 25 gallon aquarium drops to as low as 5.5, and during the day around 5.9. I was using CO2 injection, but have given up on that for the time being. I really wish I had some more buffering capacity.

Very great video, loved that you showed some of the US map zones too

Wow! so much good information in this video it's mindblowing

this explains so much man my ph out of tap is around 7.4 and the water in my tank is often 6 or below because i have driftwood. nw florida is trying so hard to kill my fish

This was very helpful. The map was especially interesting. Thx!

Thank you for the great advice

Great video my dude!!!!

Very informative. Thanks Jason.

Very good info and well presented. Thank you for sharing your knowledge.

Jason - I have to thank you for this video because it has helped me tremendously in figuring out why I've had issues with my aquariums. I live in NH and set up 2 smaller (5 and 10 g) tanks for Bettas in April 2019. My pH plummeted down to at least 6.0 after registering in the high 7's at water change consistently. I bought an API test kit but never checked my water hardness. This past month I lost both of my Bettas within a week of each other, from what appeared to be separate issues. The first had swim bladder problems and I was doing regular water changes to try and help after doing salt treatments. Not realizing that was doing more bad than good because the pH levels were obviously becoming extremely unstable. After I saw the alkalinity map you posted, my heart sunk because I'm in an area in the country with probably the worst alkalinity issues. I seriously had no idea. But on a good note, I set up the 5g tank again and have started to use a remineralizer to increase GH and a KH buffer to help stabilize the pH levels. So far it's working very well and my pH has settled around 6.6 and my dKh is around 6 and dGh around 4. Also because my tap water is so soft, I now premix the water change water and let it sit for a couple of days to stabilize before putting it in the tank. Hopefully this will give my new little guy a better chance at a healthier life than my previous 2. Its sort of overwhelming to deal with all this chemistry but it's really necessary unfortunately. Sorry for the long winded post but I just wanted to say thanks for all your knowledge.

Really good explaination, thanks

Great info and great looking fish room.

Very interesting cause our water here In Oahu tests high PPM very hard water, I’ve been needing to experiment a lot throughout my learning journey😅

So helpful. Thank you so much

Thank-you very much for making this video, it helped me get closer to understanding water hardness. I wonder whether it would useful for fish and pet stores, and online websites, to display these maps? Would it be a good idea for prospective entrepreneurs, or folks selling fish, to consider this, since it pertains to potential customers and the local fish market? Although the the maps surface water may not match tap water, nor some deeper wells, as others have already commented on.

So glad I found you. It’s been difficult finding someone with you education and knowledge in relation to the aquarium hobby. Thanks so much

Bro, sooooo helpful! Thank you!

Thank you for another great video! Very informative 😁

Nice to see you’re from Chicago! Same here

Great video! Very informative. Thanks

As usual, expertly explained!

Another very interesting video,like the way thing are explained for lesser fish experts to understand.🤔

This video was extremely useful thank you!

Great video. I live near you in the se Wi area and want to setup a tank for tetras. My size is a 55 gallon. My question is are the tetras we buy in our area at all accustomed to the hard water or should I do something to help when setting up my tank. Any info would be awesome.

Oh thanks for explaining the ppm vs degrees i was looking at hard water tetras and they all said 5-20 and my test says that my water is 300 and i was getting frustrated

Informative as always.

The most important thing we dont think about but its wat we should know but rarely spoken about in the aquarium hobby❤❤❤

i commented on your most recent video how id like a video about some of the science behind hardness and you replied back with this link, it was great... i got the fritz pack of catappa leaves and cones and such and added more then what is recommended on the box to my tank and it brought my pH down from 7.5 to 7.0 when i was told it could drop my pH to 6.0 its cool knowing KH plays a roll in how much stuff like that will drop your pH

I live in Oregon, my water is extremely soft. 0 on the hardness scale. Tap water comes out at 7.0 but if you fill a tank and test it a week later it will be around 6.0. this isn't good if you want most fish, plants and especially snails. What I did to buff my water is I add 2 tsp of cichlid salt to my 55 every water change/week. This works for me because 2 tsp isn't anywhere close to enough to make the water too hard for example it recommends 1 tablespoon per 10g to make water appropriate for cichlids. Now my PH stays at 7.6, KH stays at 80, and GH stays at 100. This worked for me, now my snails, fish and plants are all very happy, would recommend.

Thank you so much!

Super useful video! If I was using pure rodi would crush coral be enough or should I add additional products ment to remineralize rodi water?

Great explanation on this subject Keep up the great work

Really great video, thank you! I've been keeping fish for a few years, and while I did test the pH, GH, and KH of my tap water, I never bothered to test my individual aquariums. Turns out I have at least one aquarium where the GH and KH have dropped by almost half (pH exactly the same though)! This may explain my mystery snails dying. Hoping something like Wonder Shell might be gentle enough to raise the GH and KH without bothering the pygmy cories.

Recently got back into the hobby and went from a 33L as my big tank 2 years ago to a 125 with a huge sump. I listened to videos like this and so many others and decided that stability was my missing factor. It's so true. Did RO water with a ATO/AWC and pull out about 10% of the water a day, refilling with the RO stuff. With the sump loaded with cycled material and water that is practically identical every fill It's so much easier. 0 nitrite 0 nitrates. Now I just gotta decide if some uncertainty with adding hardness back in is worth it.

Very informative. I do have a question concerning when to check the PH. Do I want to check it still after it has been sitting or once it is oxygenated? The PH always rises once agitated so concerning the fish do I concentrate on the still water pH or the PH that has been agitated or oxygenated. Sorry if this question is repetitive.

I wish I knew this sooner... I accidentally killed my betta because the water was too hard 🥺 I think I’ll just stick to mystery snails. It’s super hard to manage it both for a snail & betta.

Jason, great video. Very informative. Nothing else like it on RU-vid. Keep up the great work. One question, if a fish was bred in water different than its native habitat would it be better to keep them in the water they were bred in or change to their native water parameters?

Another great one!!

Expertly explained.. The only thing missing was a chalk board behind you. You would make a great Professor.

I went from living in a state with "moderately hard water," where I could add IAL and see an effect on the pH, to living in a state with "extremely hard water," and not understanding why nothing is working to lower the pH. I figured it had to be the hardness preventing the pH lowering, and you confirmed it. Guess I'll start mixing RO water

You are my go to guy! You helped save are Molly family

Thank you! I have been so confused with alkaline vs kh and it's links to PH.

Thanks 😃

When things go south, you can always trust primes videos for answers

Great info but my head is spinning. I love the maps that was awesome. Thanks!

Why I gotta be in a red zone! ;.; I just got into this, and have major water hardness, so here's hoping I can get this sorted.

Feel so much better about my water. Getting back to keeping fish after many years.

Im so glad i found this video as im a complete newbie. But i want to be responsible because fish and aquariums, any aquatic creature is beautiful. And I would not want to harm it. Some other people just do basic care because like fish dont matter, but to me, they do. So everything i need to know everything!!!! Im in the process of a tank cycle currently, no live creatures yet. I pray I'm doing it right. I even know how to help sico fish now. Buuuuut the one thing i haven't studied is pH levels and strips and what they mean and what to do if it has a bad reading. So thanks for the tips. I may come back and re watch again just so iy sticks in my head.

This was the best video I've ever seen about water hardness! Thank you for uploading, and taking the time to explain this concept. I feel much more confident and educated now when it comes to monitoring these parameters in my own tanks.

Thank you. I've really been working at understanding this. I think it's important that I have a working knowledge of PH KH and GH. these are just the basics of "know your water - from your tap and in your tank" .. I don't need the rocket science. I just need to know enough about these to work with it .. I got an understanding of GH pretty quick. - mineral content - simple enough. I thought I knew what PH is, but I didn't really. & KH was confusing me .. the way you explained how KH = buffering stability, and directly effects PH, finally made it click .. Again thank you a whole bunch ..

In my experience wood will release a lot of tannins when first added to a tank. However, that drops off dramatically after the first few weeks.

I have a Water quality question. I live in Montana on a Private well. Our Well Water is high in Iron so we have to have a water softener system set up, now the issue is it’s now fairly salty. Since no one likes drinking our tap water I have a Brita filter on my sink down stairs to fill up jugs. SO I now have issue as far as which water to use and if there’s a fix for it. My Brita faucet is very slow flowing, so to fill my 30+ gallon it’s faster by hose which is well water (iron) or Tap water (sodium) - is there something I can do to tackle my issue without having to spend loads of money like setting up a separate filtration to fill and do water changes. My last house had a softener system and wasn’t that bad as far as sodium taste, this one seems way stronger I think because of the iron levels

Hello Jason, I’ve emailed you this already but posting it up as a comment to see if it reaches you and hopefully you get the chance to answer. Not sure if you’ll read this but this is going to be a rather long question. I live in New Jersey and I have a 36 gallon tank with 4 common goldfish ~3 years old. Originally they were in a 10 gallon tank and were passed onto me by my girlfriend’s family. Ever since they got them when the fishes were babies they have been using the Costco Kirkland Bottled Water. For a long time they were in a 10 gallon tank but I recently decided to get them a bigger tank because each of the fishes require about 10 gallons. Upon her strong recommendation I have been using the Kirkland water as well. Recently through watching your videos, in the new tank, I have finally been able to regulate ammonia, nitrite and nitrate levels. I have a fluval HOB and a 40 gallon hydro sponge filter with the aquarium co-oo air stone. I also have 6 small plants that goldfish fish don’t like to eat(Java Fern, Amazon Sword, anubias). Trying to accumulate taller and bigger plants soon. I just recently did a water test(2 days sgo). Results for which were(After a 25% water change last week because I had high nitrate- 80ppm): Ammonia: 0 ppm Nitrite: 0 ppm Nitrate: 40 ppm I recently got API GH and KH kit. Right when I did the KH: 1st drop the water turned light yellow. Which means about 0-1 degree KH. Again, I don’t use tap water but use bottled so far. I guess the bottled water is very soft. GH: Took 3 drops to turn the solution green. Which means about 3 degree GH. Given all of the above: 1. How can I transition to tap water and make it safe for the fish, what exactly product(s) would you recommend to use? What % parts should I swap the cured tap water with bottled water and how often to do the full swap? 2. After transitioning to tap water, how do can I increase the GH/KH suitable for common goldfish? Is crushed coral the only answer considering how soft New Jersey water may be according to the map in your video? 3. Would you be able to recommend any bigger/taller plants that goldfish don’t eat up? 4. Any other tests I should be running prior to doing anything? 5. My fish do not seem stressed to me at the moment, no lethargy or not wanting to eat. How can I know if they are stressed given the current environment? 6. Currently I only feed them Tetra Goldfish Vitamin C Enriched flakes - normal amount in the morning and a little in the evening. Should I be feeding something else? Better? 7. My nitrate never seems to be under 40 ppm. Granted I’ve never tested the water right after a partial water change. How can I keep it on the lower side? Is more water changes my only way to go? Jason, if you do get the time to read this comment and answer my questions, I will really appreciate it. If you don’t mind telling me the exact products to use, that you have tested or known of, that would be really helpful. I’ve always enjoyed your videos and the amount of scientific detail you give to your viewers. I am new to the hobby but I feel that you are helping me catch on daily quick. Thank you for your time and I look forward to hearing from you.

Thank you for the info! I noticed a difference in tap water hardness just moving from one side of my city to the other.

Ive learn from old chinese, need a good substrate atleast 4 inch, and keep ur ph at 6.8 add live plants and its will be easy aquarium care. Ive notice a big change in my water with nitrate and nitrite now gone. I add almost same water propriety as my aquarium. Just my hardness is at 200 rn, and water i add is at 100-120, so ill need to look my chemical i add for plants might be not good. Hope hardness variation change wont affect my fish. You're very talented for explication. Keep ur good work👍

Great video!!! Thank you for sharing Jason!! awesome stuff :)

Ayeee! You're from Chicago region like me! Thanks for the informative video really helped me understand

This is a great and informative video. I agree that, for the most part, you are better off not messing with your water hardness parameters. You are chasing the proverbial rainbow. Stick to fish that are good across a wide range of parameters and that are locally bred. I have Kribs constantly spawning in 18 dgh and 7.6ph. Plant growth seems to be far more of an issue for me in hard water.

Your presentation is thorough, and happily, within my capacity to grasp. Thanks.

👍 Thank you, Jason.

Great info thanks for sharing

Once again great and informative video!! On e question unless they are wild caught fish aren’t many fish raised in neutral water? Thanks 😁

I live in the middle of nowhere PA and this made so much sense. My ph is at about 6.4 and the ppm and dh are all over the place. Our water comes from a local stream and they constantly are changing things up and adding to it. My ppm was through the roof in my planted endler tank so I went out and got some distilled water. Is that what I should be doing? We have eo many natural springs and I thought about going around and testing those lol. I have many 5 gallon buckets. I know everyone races about api test kitsch but is there something better? You have easily become my favorite fish RU-vidr. So helpful!

Amazing content as always Jason. Thank you. I have one question. In Sydney (Australia), tap water is quite soft. Kh is close to zero, GH is circa 50. But when I test the GH in my tank, it's quite high, around the 180 mark. Is this being caused by evaporation? If evaporation removes the water, then concentration of magnesium and calcium would exponentially get higher and higher with each water top-up, wouldn't it? Unless our top-ups are always done with distilled water. From your vid, my understanding is that adding distilled water may further lower KH which is already dangerously low in sydney.... Appreciate any advice.. 🙏

I have a 10 gallon. My tap water shows purple on the test strip 300 mg/L GH. And my tank water is purple on the test strip and at 300 mg/L in red lettering. Also KH was a little high in the tank, 180 was that number. Should I take out the volcanic lava rocks from my filter? And are fancy guppies ok at that level or do I need to get a different kind. I only have two snails in there. I want to add 9 guppies and three cherry shrimp. I'm growing grasses to add before. I have 7 marimo balls in there. Gravel and smaller rocks a piece of driftwood and an air stone and manmade rock hideaways are also in there. Any advise would be greatly appreciated.🙋‍♀️✌

I learned a lot thank you

This is interesting

Hello. Just stumbled on your video. I heard you say you were in the Chicago land area, I live in Lyons, IL and would like to know if you also have any shops that are open. Would like to check one out if possible. Loved your explanation on water quality. Thank you for posting these instructional videos.

I'm in the North Central Texas area where our water comes in cubes not because it's frozen but because it's got so much mineral content, lol. Out of the tap I have around 100kh and 150gh but a nice mid-range ph of about 7.3-7.5-ish. Which will be good for the Platies and CPO dwarf crayfish I want to try to raise but a bit hard for Bettas. I could probably stand to soften it a little bit probably but not by much im thinking. Honestly it's probably better than whatever they're floating in at Petsmart in those little cups.

Great video. I live in Central Florida and I have a Crawfish. I’ve had him for about 3 months now. He has molted once. Can u do a video on Crawfish care and water conditions?

Great video, thanks! I was just reading about this from a fishkeeping book I picked up at my library, but your explanation is much more easy to follow than the book.

Hi Jason....thanks for your time explaining the water hardness here @ youtube..question I have? what can cause kH hardness to jump from 6deg ( 107 ppm) in tap water to 9deg ( 162 ppm) of kH in my planted tank??? no wonder my co2 system does not move the pH level at all...the buffering factor is over the chart...I do fertilize with micro and macro daily....ammonia 0, nitrite 0, nitrate at about 20 to 30 max, pH of tap water about 7.5 ??? What can be a cause of the kH increase in my tank??? 6 deg is high enough...9deg is way too much THANKS

Best discussion I've seen on this topic in a long time! Great site, thank you.