I just joined the forum and I'm hoping I can get some help with some issues I've been having.

I have a 20 gallon freshwater set-up with five Serpae tetras, four bloodfin tetras, three zebra stripe danios, a sunset fire platy, a swordtail, and a new honey gourami (along with countless snails that keep breeding). I recently added three of the bloodfins and the gourami to my already established tank. I'm running an Aqueon Quietflow 20, and have an appropriate heater. The tank has a few hiding places, but I plan on adding more vegetation when I have the money.

The issue I'm having is dark coloration showing on the gourami's head area coupled with it not coming to the top during feeding. I have seen it nip at some food and spit it back out, but never eat it. I've also seen it nip at some algae on the plants. I know the honey gourami is a shy breed, but I'm starting to worry because of the eating issue. I think that the discoloration is due to nitrite/ammonia burns, so I did a 70% water change and added ammonia neutralizer to the water. I also started slowly adding aquarium salt in the recommended dosage to add electrolytes and help gill function. The ammonia neutralizer seems to have worked because the dark coloration isn't spreading (it might be getting better, but I'll have to wait and check on that). I've also started to be more patient with feedings and not over-feed to curb ammonia build up. I feed my fish flake food and occasionally a bit of frozen brine shrimp.

Are gouramis more susceptible to nitrite burns than tetras? The bloodfins I added the same day as the gourami haven't shown any signs of burns or odd behavior. They're doing very well. Should I be worried about the gourami or try something different? I don't think that it's new-tank shyness anymore because it's been almost a week.