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Nitrites and what to do
Sounds like your tank is still finishing up the nitrogen cycle process. Here's a good article that explains a bit more on that:
The Nitrogen Cycle
The end stages of it, nitrites will spike high, then start falling, and nitrates will start showing up, and eventually the nitrites will go to 0 ppm. When ammonia and nitrites are at 0 ppm, and there's nitrates present, the tank is finished cycling.
Nitrates are fine, the only thing is you want to do is ideally keep them under 20 ppm-so yours is fine and no need to worry about them at this point. Ammonia is very toxic to fish, nitrites are toxic to fish as well-though not as bad as ammonia, but still not good. Nitrates are slightly toxic at higher numbers.
What chemicals are you using to "lower" the nitrites? I can't think of any that really will do that. The only one I recommend is Prime by Seachem, and it converts it to a nontoxic form without removing them, so the tank can still cycle. And, you will still show those present in the tank-because it's not removing them, kind of like a false positive.
Depending on the types of fish you have, 1 tablespoon of aquarium salt per 5 US gallons of water, dissolved in some dechlorinated water and added into the tank is good for helping the fish cope with nitrites. Tetras, loaches, plecos, catfish, or any scaleless fish are all sensitive to salt, so not a good idea to use salt with them. If you don't have those fish, go ahead and try the salt. It won't remove the nitrites, but helps the fish deal with the nitrites. Nitrites inhibit the fish's ability to absorb oxygen into their bloodstream. Something with the salt combats that.
So....if you have all "safe fish" not on that list, try the salt. Or, go with the Prime by Seachem option to neutralize the nitrites. If you go that route, be sure to add it to the tank every 24 hours, because it dissipates after that time.
Christy
