Ok, here goes. I have a 10gal freshwater tank up and running for about 2 months now. All my water levels have been great until about a week ago. I have 5 small Mollie fish since we started. For the last week I noticed that my nitrite levels spiked and NOTHING seems to help. I have performed weekly water changes and cleaned (2 grow to be 1.5", the other 3 grow to be 2") the tank glass and gravel. When the levels spiked I researched what to do and this is what I found and did. I am afraid I did 2 things wrong in the above time frame (1) rinsed the nasty black sponge in 1st filter and (2) my son and I accidentally both fed them days in a row so they got more food than normal.
1) 20% water change and tank was clean on day 1, 2, 4 and 45% change late on Day 6 (today) as per pet store advice
2) added and extra air pump and air stone
3) added Aq salt
4) tried Prime
5) I changed the filter to a 4 stage filter instead of a 2 on day 5
6) added some bacteria (bottle form) today
All levels still show in safe ranges except the Nitrites. The Nitrites are coming down after today's change but are still in stress area at about 3. What can I do or what am I doing wrong. Can someone help me?
The pet store said the nitrite issues the fish could be fine one day and be dead the next without any signs or symptoms. Is this true?
First of all, good for you for checking your water quality!
It sounds like you're doing everything right, so I have two possibilities. First, are you feeding them too much? Uneaten food pollutes the water as much as poo. Second, is your nitrite test out of date? It's possible your test kit is bad - maybe it was on the shelf for years at the pet store (since most people don't use them).
Is there gravel in the tank? If so, there will be good bacteria living in it, even if you wash out the filter. Try to vacuum just a portion of the gravel with each water change.
Any chance you can add live plants? Java fern is pretty foolproof, and will grow without a lot of light (though you shuold probably put the aquarium light on a timer). The plants will take up the nitrite, adding a margin of error in the system. You still need to do regular partial water changes, of course, but the plants will help keep things stable - and the mollies will love them!
If the chips are down, the buffalo is empty.
What sort of test kit are you using? Test strips are notoriously inaccurate. I think one of the most accurate ways to test water is with the API liquid test kit.
I have found really fabulous aquarium advice on the online forum aquariacentral.com. They have a newbie forum and you can read there for days and really learn a lot. There are very passionate hobbyists there and you will definitely get good help.