SCUGrad

While the forum was down (actually a bit before it), I experienced a rash of fish deaths in my 75 gallon tank. I lost:

4 neon dwarf rainbowfish
2 swordtails
1 clown loach
1 bristlenose pleco

At first, I blamed the BA tetras I had (see this thread: Killer BA Tetras?) but the local aquarium expert ruled it out because the other fish showed no signs of abuse. Especially the two large platinum angelfish which would have shown the first signs of abuse.

I tested the water parameters and found a very high pH (8.8) and high carbonate hardness (11 kH). I've done two water changes since then and now have a pH of about 8.4 and a carbonate hardness of 8 kH. I've learned that high carbonate hardness tends to lead to high pH. To lower the pH effectively, I need to lower the kH through water changes preferably with distilled water.

Just wondering if you guys have any thoughts:

1. Do you think the fish deaths may have been related to the high pH?
2. If I need to lower the pH, how do I do this (I don't want to use peat because it discolors the water)and how low must I bring the carbonate hardness to be able to lower pH effectively?

10gallonmadness

It depends. If the PH fluctuated (spelling?) to fast you fish could have gone into shock and died. But I doubt thats the case.
To lower the pH you could try putting a piece of driftwood in, but the tannins would eventually run out. Probably, the best way to lower pH is to used crushed coral. You could probably get a couple handfulls from your LFS.

SCUGrad

There's actually a fairly large piece of driftwood in the tank but I think all the tannins are gone. Crushed coral? I think that adds to the carbonate hardness of the water, right? I could be wrong though...

pepetj

I agree with you here. At this high end (relatively speaking) pH swings are not likely to happen. The buffers you have with KH over 3dKH is usually considered as safe for pH stability (I run two soft/acidic tanks with 2 to 2.5dKH and pH of 6.5 to 6.8). Driftwood would run out of tannins eventually, but it takes some time for that to happen. It will taint your water (I love the looks of it but some don't) unless you use, and replace accordingly, activated charcoal.

Actually crushed corals would end up raising pH, not lowering it.

Please note that pH measures can have a significant error due to dissolved CO2 or O2 in the sample, or possibly, by decaying quality of reagents over time.

To be sure, take some water from your tank and let it sit in the test vial for an hour or so. Then add the reagent and check how it goes. It is sometimes a good idea to double check the reliability of your test by using another test and compare results. Even pH meters can give false readings if not regularly cleaned (the probe should ideally rest in distilled water when not in use) and calibrated (even then the buffer solutions could be damaged due to exposure to atmospheric gases).

Most fish should adapt to pH a bit higher than their ideal range. Stability is the most important issue. That said, it is normal for pH to change through the day. Measuring pH early in the morning is a good idea since at this time you are likely to get the highest peak attained by your tank.

Are your others parameters OK? How old is your tank? time usually brings down KH as well as pH, as carbonates are used (even depleted if no water change is performed) in the life process going in there.

Pepetj
Santo Domingo

SCUGrad

Thanks, Pepe, for your well thought out answer.

The tank has been running for about a month now and is cycled. I don't use an electronic probe to get pH, I use test reagents. The reagents are less than two months old so don't think you'll have a quality problem. My other parameters are ok.

I will try your suggestion of leaving water in vial for an hour and see if that changes the result any.

All that said, do you think the high pH I measured could be responsible? I do agree that fish generally adapt to the pH of their water

10gallonmadness

Ahh! Sorry I got mixed up...

Shawnie

are you using stress zyme and cycle in this tank as well as your other tank?

SCUGrad

No