QT/Rx tank

[clines4]

I have a 10 gal qt/Rx tank that has been running for over a month. I started it with my tank water. No rock, sand , nothing but 3 stage hob filter. I kept a few fish in there before placing into my tank, about three weeks ago. I checked water today, ph,sg,nitrate,ammonia all good. Nitrite is 10+! I've changed small amount of water one week ago. What could cause this? Do lights play a role? I don't run the light unless something is in there. I don't understand wuz goin on.

[HighlandReefer]

You have ample Nitrifying bacteria in your system which will brake the ammonia down in fish wastes to nitrite. This is done in the presence of oxygen. You apparently do not have enough Denitrifying bacteria which brake down the nitrite to nitrogen gas. This process is done in a place where there is no oxygen like a sand bed or live rock. Macroalgae will take up the nitrite if you add it to the aquarium.

FWIW, nitrite is not toxic in a saltwater aquarium like it is in a freshwater aquarium.

[clines4]

So it would be okay, IYO, to still use as treatment tank. Especially after a 50% WC.

[HighlandReefer]

Yes. ;)

Watch your ammonia, it is the most dangerous to your fish.