pH crash in QT tank

[briannesbitt]

So in our attempt to provide a nice little hiding spot for the panda corys in our QT (5 gallon) tank we added a small ABS plumbing tube give them a cave.  I think this lowered our pH and caused what was a cycled tank to stop consuming the ammonia (I think).  Quite the controversy on ABS but seems the general consensus is PVC is better?!?

I also noticed our tap water has changed since spring ... but we did a quick test.  Tap water is now about an 8.8 pH.  After being left out in a bucket it drops to about 6.8 but if the bucket had the ABS piece and left out the same amount of time it was 6 (the lowest our test shows so maybe it was lower).

Before this event our tank was always showing 0 ammonia, 0 nitrite and small nitrates (seeded filter with media from our main tank).  Now our ammonia is about 1 ppm but with the low pH I understand that its mostly ammonium which isn't harmful.

I think if we bring the pH back up too fast that ammonium will go back to ammonia and being harmful.  Where should we go from here?

Our thoughts is to use an ammonia remover HOB (AC 20) filter insert and then do twice daily 20% water changes to try and get it corrected.  Our current QT tank mates (1 pearl, 3 panda corys) seem to be doing fine and have been in there for over 2 weeks now.  We could just move them to the main tank but I think that would be a bit of a shock with the pH change and I think getting the QT fixed up first might help their transition.  Maybe its better to just move them over and then re-setup the bare QT tank for the next group.  Using a trickle water adjustment over 30 minutes for the fish might be ok?!?

Note: I know the ammonia remover is not a great long term solution but realistically this is just our QT and will get shutdown in a couple of more weeks as the main tank will be fully stocked so I'd rather just keep the water safe in the mean time and not worry about if the cycle is going or not.

[exv152]

It's most likely your ph dropped below 6 if your test kit only reads as low as that, and you're getting ammonium readings. Nitrifying bacteria need oxygen to survive and there's less oxygen in lower ph, and the lower your pH goes the more the nitrifying bacteria begin to die off, which is why you're seeing ammonium. But as you said, NH4 is not as lethal as NH3, but you can render it completely harmless with some seachem prime. If you were to test your KH I bet it's practically zero. Water changes will help increase the KH in your tank which should stabilize things a bit more. But don't do huge water changes, 25% is probably good enough, unless the KH in your tap water is low too. I always measure KH in all my tanks for precisely this reason. It's a test kit more valuable than pH in my opinion. I don't recommend messing around with the pH too much, and especially the use of ammonia removers, you're better off understanding why the pH went so low in the first place and taking it from there.

[Fishnut]

Take out the pipe and put in some driftwood or rocks.  There are so many natural aquarium things out there that there's no need to screw around with an un-proven material.

Never add an amonia remover.  You'll arrest your cycle and make a bigger problem.  Take out the pipe and do water changes.  Add a natural hiding spot and try not to worry so much about the PH.  I would suspect that the amonia is more of a result from over-feeding than anything else.  I haven't tested my PH in forever.  I do regular water changes and try not to over-feed.