Nitrites Up After Tank Cleaning

[Gvilleguy]

I have had fish in the tank for almost three weeks (zebras and glofish).

1. After day 7 I did a 25% water change with a gravel siphon to bring down the nitrate level, which was at 40 ppm. I cleaned the gravel with the siphon, but only half of the tank. (that's all I could do before 25% of the water was sucked out)

After the first cleaning ammonia and nitrites remained at zero every day.

2. After day 14 I did another 25% water change, and this time I siphoned off the gravel on the other half of the tank bottom. I also took out several fake plants, and a large, fake cave/island decoration. I rinsed these items off in the bucket of tank water that I had removed, and used my fingers to rub the cave and plants clean. (I did not really see much of anything on them, anyway)

It has been 4 days since the second cleaning, and ammonia = 0, but nitrites have been 0.25 ppm every day. So this morning I did a 50% water change, with no cleaning or siphoning. Nitrites still = 0.25 ppm.

So I guess I killed off some nitrite processing bacteria on that second cleaning, yes? I suppose next time I should rinse off the decorations, but not rub them? Or should I only siphon gravel every few weeks and not during every water change?

The danios do not seem stressed yet, but I'm wondering how long I should go before doing a larger water change to try and bring down the nitrite levels.

 

[Mikaila31]

do a 50% WC then test with a liquid test kit. Also what dechloro are you using on the tank, or any other additives.

 

[Gvilleguy]

That's what I did - a 50% water change today, and then tested with API Master kit. It's showing 0.25 still. Are you suggesting a second 50% change?

I have no additives in the tank other than "Top Fin" brand dechlorinator, which I added with the new water this morning. The KH of my water is zero, and pH is around 6.8 usually.

 

[OldMan47]

A simple water change will only reduce chemical concentrations by the percentage of the water you change. If you do a 50% water change, you can expect to reduce chemical poisons by as much as 50% (a lot depends on the concentration in your tap water). If your test kit can only show 0.50 ppm and 0.25 ppm, it will be hard to tell where you actually started between those readings. After a simple 50% change, you may not be able to discern the change that actually happened in terms of the test reading. On the other hand, the actual change in chemistry will be felt by your fish. A change of far more than 50% is what I do whenever my chemistry gets out of control on a tank. I find that a 90% or more water change with dechlorinated, temperature matched tap water is very well tolerated. That means that in a situation like yours, I would do a 90% water change and fully expect to reduce poison levels to almost nothing (a 90% reduction). I have used this approach on a number of occasions and the fish always told me, by their actions, that I had done the right thing.

 

[Gvilleguy]

Well - an 80% water change this morning temporarily put nitrites almost to zero, but by tonight they were registering between 0 and 0.25 again. I definitely killed off some portion of my i-bac colonies! We're going to test the nitrite tolerance of my danios now, as I won't be able to do another water change for several days. I hate putting the little ones through a mini-cycle!