sick aquarium help

Question
I have a small 10 gallon tank, and I have only had it set up for about a month. It has an under gravel filter, fake plants and a fake log to hide in. I do 10-15% water changes once a week. I use a siphon hose to clean out some of the gravel. I got 1 dwarf gourami, three tetras, and a really small pleco. The gourami got some kind of body fungus and I was advised to treat them with maracyn. The gourami got better but then died two days later. Now the tetras that used to be buddies, are now being kind of aggressive. One chases the others around. I know this causes more stress and don't know if I should leave him in there or not. All of them are hanging out in the lower part of the tank (closer to the bottom than before) and not eating as much as they used to. Should I take all the fish out and clean everything thoroughly, or will that make things worse? I don't know what to do to make them all happy again. Please help

Answer
Hi Kate,
I'm sorry to hear your gourami died. Poor thing. He may have just been too stressed from the illness.

One thing you should definitely be careful about is I would test your water if you can for ammonia, nitrites, and nitrates. Because medications can sometimes severely deplete or even just destroy the beneficial bacterial or your biofilter. This will cause a spike in ammonia which can be very very dangerous to your fish.

I'm not sure what species the tetras are. But many tetras tend to be slightly aggressive towards each-other. A pecking order is all it is. They constantly remind each-other who is boss. Sometimes it really helps if there is at least 6 tetras of the same species living together rather than just two. Its better to have several individuals to distribute the pecking order rather than just one on one.

But make sure you test the water if you can. And if you can't test the water just yet. Do a water change. It's the best thing you can do for your fish and wont hurt just as a precaution. A good 30-50% water change is best. Just as a reminder, always make sure all new water is dechlorinated with a good water conditioner and close to the tank temperature as you can get it. A little warmer is fine if you can't get it exact. But not too warm and not colder definitely.

If it turns out you do have ammonia and nitrite readings (these readings should always be as follows- Ammonia-0 Nitrite-0 Nitrate- 20 or less) then the best thing to do is a water change to bring it back to the safe zone and use a water conditioner that neutralizes ammonia and makes it safe. Amquel+ and Prime are very good for this. And eventually your biofilter will re-establish.

Best wishes,
Karen~