Sick rainbow fish

Question
Hi Chris,

I have a 20 gallon community tank that I have had 6 months.  It was purchased from a friend complete with fish, which she had maintained for over a year.  It has a whisper filter for a 20 gallon tank.  the pH is 7.0, ammonia and nitrite 0.  I do 25% water changes weekly.  I started with 2 tetras, 1 opaline gourami, a three-inch rainbow fish, 1 platy, and 1 clown loach.  A few weeks after purchasing the tank, I added 2 new tetras.  One of my original tetras died within a few weeks.  Then the two new additions.  Then the remaining tetra.  This was in July/August.  I figured I brought something in with the tetras I purchased... needless to say, I won't buy fish from that store again!  A few weeks ago my platy died - he started hiding at the bottom, stopped eating, started breathing with his mouth open, and then died.  That left me with my gourami, rainbow fish, and loach.  About a week ago I noticed that my rainbow fish had some type of infection on his mouth, it looked like his face was being eaten away.  He also has a large round mass behind one of his fins (he's had this for a while, doesn't seem to bother him).  The other two were normal.  I started treating the tank with Maracyn, as I had no way of separating the fish.  Rainbow fish did not improve after 5 days of treatment.  Then the loach started staying at the bottom, not eating, rapid breathing.  I figured he was sensitive to the medication.  I purchased a new 10 gallon tank and set it up as a quarantine tank (I know, should have done that months ago when it all first started), moved the rainbow out, did a 25% water change on original tank.  Loach died on Saturday.  Now gourami has 20g tank to himself, doing great.  Rainbow fish has 10 gallon tank to himself, he is mainly staying at bottom of tank, rapid mouth movement when breathing.  He does come up to eat at mealtime.  I have been treating the 10g tank with Maracyn and Maracyn 2, plus Coppersafe, all per manufacturers instructions.  Will do 25% water change on Tuesday and continue treatment for additional 5 days.  Both tanks are treated with StressCoat.  When I set up the new tank, I used 5g from 20g tank and put a handful of gravel from the 20g tank to help start the biological filter and used stressZyme.  Water quality in new tank has been okay, low levels of ammonia but I treated with AmmoLock.  Nitrates and Nitrites still negative.  Basically, I have no idea what is wrong with my rainbow fish (I'm assuming bacterial).  His head lesions seem to be gone, but he still stays at bottom of tank with rapid breathing, dorsal fin clamped.  Any ideas?  Thanks.

Answer
Hi Christina;

Whatever it is has probably been treated successfully by the medications. The rainbow may have had some damage that may or may not resolve. Sometimes we just can't see what's wrong because it's inside and it can even be several problems combined. Swim bladder failure, heart damage, kidney or liver dysfunction and/or gill damage that prevents proper oxygen absorption. They are all possibilities. The best you can do is continue to provide a healthy environment for him and hope that he recovers.

It is even possible that the gourami has played a part in all this. They can be very aggressive fish and sometimes bully your others without knowing it's happening. If you are certain your gourami hasn't been causing problems, you could re-stock the 20 in a couple of weeks. Just do it very slowly, waiting at least a week after adding a couple of new ones. It would be good to use the quarantine tank though, if you can. I guess it depends on what happens with the rainbow. I wish I could help more on that. I just don't know for sure...

At Your Service;
Chris Robbins