Sick fish? Tank nitrite level trouble?

Question

Ok so this is a long and complicated question. I have a dwarf gourami who doesn't seem to be eating and hasn't in about a week. I've had it just over two weeks. When I first brought it home, it didn't eat for a few days but I thought it was just adjusting. Then it started eating for a few days and then stopped. I hides almost all day and never comes out. When it does come out, it seems ok. Maybe it's losing a little color but it doesn't seem weak or ill. Also, none of the other fish seem to be picking on it. Could the nitrite levels in my tank be a factor? I have a new 10 gallon tank and when I added fish two weeks ago (3 tetras, 1 gourami, and a swordtail), I added a 30 gallon dose of bio-spira. The package says you can't over dose and you should use the entire contents of the bag. The 30 gallon dose was lowest dosage the pet store had. It worked great at first and within a few days I had nitrites in my tank. They raised up to 5 ppm, which is the highest my kit....

Answer 1

do a 25% water change and reduce  or stop feeding until the nitrite levels drop. if this is a new tank you will get peaks in the water quality until the filters mature properly.

Answer 2

Ammonia and nitrites are toxic to fish, you should keep each below .25ppm. Do a partial water change to reduce the nitrite levels. The bacteria will attach itself to any decorations, gravel, inside the filter, etc, so you don't have to worry about losing the bacteria. All you are doing is reducing the toxic substances so they are less harmful to the fish.

Answer 3

Your aquarium is seriously overstocked and not cycled.  The packets they offer only speed up the process.

Do water changes and return at least two of the fish to the store.

UPDATE: You don't have to worry about disrupting the cycle in this case.  The reason this is sometimes recommended is to keep the ammonia and nitrite levels from dropping too low.  That is clearly not a concern here.  If your filter uses activated carbon I would replace it immediately.  Be sure to only use dechlorinated water.  Doing this by aging the water for two days in an open food safe container is preferrable.  However in your case I would recommend a dechlorinator available at the pet store.