Why Does My pH Go Up In This Tank? 

I love how natural your tanks look

Hi Dan. I have a South American Tetra aquarium. I like the low acidity for my fish and corydoras, but I read that too much aeration will lower the Co2, and raise the pH. I remedy this by consistently adding natural liquid tannins, Roobios Tea, and leaf litter. I want that aeration regardless, so I just do a bit more maintenance on my end to keep that low pH. Say around 6.3+

I was going to suggest decomposing plant matter but apparently that drives PH *down*... 🤔 However, diminishing levels of CO2 can cause it to rise. I wonder if the waterfall is constantly oxygenating the water, driving the CO2 down?

Just to add to my previous message about the plants sucking up all your Co2, its a mix of highly oxygenated water and plants causing your problem, I have been in the same battle for months adding pH down but then a few hours later its back up but I have finally found a solution, I have added a huge piece of oak to replace my small piece of drift wood, and now I add alder cones which release tannins and then slowly decay on the bottom, which you can suck up later with your gravel vac and replace with fresh ones. This has lowered my pH which was off the scale 8.4+ down to 7.6-7.8, and now when I add my pH down acid it keeps its pH for longer and does not rise so quickly, takes days rather than hours.

Most water companies use ph balancers that wear off anywhere between 48 hours to roughly 10 days. After time water, results will go towards what they were prior to being chemically treated. Secondly, due to the light stocking, my thought possibly that it could be CO2 depletion. As CO2 is depleted this can cause an increase in the PH. The vinegar test isn't a 100%, especially when it comes to PH. It is a fairly good test but there are certain rocks that will not react to vinegar but will gradually increase the PH. And the last thing to consider, though unlikely though could be reset with peroxide treatment, is that certain aerobic and anaerobic bacterias can increase the PH just as there are some that will decrease it.

Hey Dan, any chance you have anaerobic zones in the tank or filter? Nitrate and sulfate reduction by anaerobes leads to pH increase. It wouldn't take a lot since your water is poorly buffered. It's also possible certain plants in there are denitrifying as well as absorbing metals leaching from the rocks, leading to pH increase. Any special plants in your setup?

it the damn stones man

I have this problem only in my planted tank, the plants consume Co2 which raises your pH. You can stabilize the pH if you have Co2 injection.

I had the same problem with my tanks when I was using RO water to top off and less frequent water changes. PH went up to 8 and higher. I had no explanation either.

most likely the lack of nitrites and nitrates will allow your pH to rise towards 8, also lack of CO2 will also raise your pH towards 8. Didn't you at one time add egg shell (crushed) to help out your snails and shrimp(s)? The soil you bring in from your garden with your plants can also have fertilizers and other nutrients that will raise your pH towards 8. 7.6 or 7.8 is ok for your fish in there. it could also be your gravel/substrate, or even your rocks. Best way to test rocks is with HCl, Hydrochloric acid. Vinegar is not the best tester. Oil shale would affect your pH from the oil in it. Regular shale I have used without any pH change, same with granite and quartz. I know you also added chicken grit/crushed oyster shells to some of your tanks, not sure if you added it to this tank. It could even be microbes and infusoria sucking up the calciumcarbonate to make shells. Most likely it is either rocks, substrate (commercial fertilized substrate) or the soil from your garden added with your garden plants.

Hey I thought I'd follow up on something related. I did your baked, ground up eggshell thing and my ph went from 7.6 to 8.4.

i tried test strips once and it read 8 which to me made no sense so i bought a Hanna ph probe tester and it now tells me 6.7/.8 ive never trusted test strips of any kind. but also dont you sometimes throw sodium chloride in your tanks? it can definitely stick to rocks and wood and linger around for a while

Have you tried testing the ph before the lights go on? I suspect that your ph is significantly lower. My 8 gallon heavily planted Walstad bowl goes through the same swing. Before lights turn on the ph is under 7. A few hours into the light cycle the ph goes up to 7.5. I believe it’s because the photosynthesizing plants are using Co2 reducing the carbonic acid in the water.

Maybe it could have something to do woth evaporatation

I just tested my tank as well and it does the same thing............ really weird

Could be your hardscape stones are leaching minerals into the water...

If its working dont mess with it

Could be your plants releasing CO2 at night. I believe It is the stone and sand. I had the same types of stone and sand, makes me think you live close... test the pH of the water where you collected them and you will find the pH is very close. The calcium and/or limestone is in small quantity and partially locked in by surrounding minerals reducing the effect. Not enough really to see a reaction but..

It's going up because your plants are absorbing all the CO2 and nitrates... that drives pH UP... If you rest it in middle of night with no light... whwn photosynthesis isn't happening...I bet your pH is a bit lower

Maybe some plant soil from the structure ??

All things water 🤯🤣

I tested today with 2 different testers api said 8.5 the other gave me 6.5😮

Interesting question. 🤔 I suspect there may be something in the waterfall structure itself, altering the pH over time. Is there a way to isolate the waterfall portion from the tank & do a trial test with lower pH water; observing the possible increasing pH, etc? Good video. 📺👍😎

Too anser ? Its tannins which are good

I am having a problem with a high ph too. My water from the tap is 7.0 to 7.2 and varies from soft to vary soft. and gh test good for the tetras I keep

Just a wild guess. Maybe salts of calcium and magnesium are increasing. Lots of evaporation. Tanks at the bottom - gets exclusive affect. Shrimp molts and dead snail shells decomposing having been collectors of calcium from the water/food over time. Much more water in than out could have an effect, but I was under the impression you have almost no calcium in your water.

Hey Dan. I was watching another YTer's video on a Betta planet aquarium, and they planted a plant exactly like what you call Milfoil. They had it listed as Green Cabomba. I suspect that is the plant you have, not Milfoil. Here is the video to see. Timestamp 7:38 on wards of this video: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-a8pi-JSi8Sk.html

Maybe too much plants decaying.

The rocks

My water goes into the tank at seven and comes out at eight. I’m just wondering if that’s too much of a swing for the fish. I’m thinking I should stick to small water changes and more often but I don’t know that’s why I’m watching your stupid video it tells me nothing thanks lol

My tap water is 7.3. My PH rises to 8.2. Don't know why?