Guppy Troubles - High pH?

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Aquarium Advice Newbie
Dec 4, 2023
We have a small 6 gallon tank we keep 3 guppies in (recently added one oto). We've had the tank a few years, after losing a couple bettas we thought we'd try guppies. We've not had a lot of luck. The first set we got from Petsmart, 2 died, we chalked it up to being Petsmart and found a local store. The 3rd guy actually just passed and we had him a year (our longest!) And seemed to have swim bladder issues? We had two other sets and they just don't last longer than 6 months (one jumped out of a tiny hole in the back, bad luck). But I test the parameters and the fish store guy told me it was OK we had 0 ammonia, nitrite, and nitrates. We keep a live plant in there. The only thing "off" is our pH is like 8.4. I added a catappa leave and it was 8.2. Someone mentioned a high level may be what our trouble is? Straight out of our well water tap it's 7.6. So how, or should, we even try to address it? Should we do more water changes (we do like once every 3 weeks). A couple weeks ago after my husband changed the water the fish seemed stressed and one died, but the other two bounced back (until this other died yesterday). I wonder if he changed too large amount of water...I think it should only be 25%? We're getting ready to call it quits because it shouldn't be this difficult! We have a 90 gallon my husband has kept for 20+ years and never had issues with...we have a parrot cichlid who actually refuses to die in there now! Keeping this smaller tank has proven to be much harder!
I would also say that your water parameters dont make sense and could indicate something is off. The nitrogen cycle takes ammonia and turns it into nitrate, but you are reporting zero ammonia, nitrite and nitrate which is practically impossible and could be hiding a water quality issue. In a cycled aquarium you should see zero ammonia and nitrite, with some nitrate. In an uncycled tank you should see ammonia and/ or nitrite depending on how far progressed your cycle is. There is something wrong with your test results.

Its possible to get your parameters if you are doing very large, frequent water changes. But you are only doing a water change every 3 weeks.

How are you testing? What test kit are you using? When are you testing thr water? Before or after your water change? Are you sure you are doing the test correctly?

It does sound like a water quality issue. Either with your cycle or the guppies dont like the well water. You could try using bottled spring water for water changes in your guppy tank. One thing is that at that high pH, ammonia is very toxic and tiny amounts will kill fish over time.
Thanks for the reply! I agree the parameters are confusing...I've gotten nitrate readings like only once in the past. I have the API Master Kit and follow the directions as written. I would test before water changes. We do have a high algae growth in there too which I've been reading high pH can attribute to? We also have detritus worms in there which I have no idea where they came from.
So next steps since the fish are already in there? Try spring water for changes? Should we even try a pH neutralizer or does that take it down too quickly for then? Do we try less amounts but more frequent water changes to see if it'll cycle?
pH has nothing to do with algae growth. Algae is the result of too many nutrients, or too much light. If your nitrate really was at zero you wouldnt have algae growth.

I would redo the nitrate test. Really abuse bottle #2. Bang it on the countertop, twist the bottle etc. A light shake isnt enough, you should see a white powdery residue in the drops which is the reagent that can get stuck to the inside of the bottle if you dont shake the bottle hard enough.

Detritus worms can get into your tank from a whole variety of sources. Maybe as larvae in some food you bought, or some driftwood or plants, maybe an infected fish. If you arent overfeeding they usually arent a problem, and if they are coming out of the substrate and you can see them, that can be a sign there is a water quality issue.

A pH stabiliser wont work. High pH is usually due to high carbonate hardness (KH). KH absorbs acid and keeps your pH stable which is called buffering. So to lower pH you first have to add enough acid to use up sufficient KH and then your pH can drop. pH lowering chemicals arent very acidic so you end up throwing loads of the stuff into the water to first overcome the KH and then drop the pH. Its much easier raise pH because that involves adding stuff than it is to lower it because that involves removing stuff from the water. pH adjusting chemicals are firmly in the category of things that dont do what they say they do on the bottle.

Also trying to adjust the pH the water wants to be at results in pH swings, and fish like stability above most other things.

The only real way to lower a waters pH is to mix it with acidic, soft water so you are diluting the buffering chemicals. This means RO or distilled water. Bottled spring water is usually on the hard, higher pH side of things, but usually somewhere closer to neutral than whats coming out of your tap, and it should be clear of impurities that might be harmful to fish.

If you are going to switch to spring water, i would do 10% water changes every day for a week to avoid those big parameter fluctuations, and then return to your normal water change routine but with the spring water.

As to cycling the tank, we dont know you arent cycled. Just that your parameters dont make sense. I would get a 2nd opinion on your water testing, the likely result to be off is nitrate, but if you are confident its zero, then its zero.
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