Red Tailed Shark with Red gills

[Finian]

Hello!
You all are going to think I'm an awful fish owner after this story, but I must tell it to shed light on the problem.
I bought a tank, cycled it, and got some fish. Two of those fish were a rainbow shark and a red tailed shark.
Ich attacked my tank, so I put lots of bubbles in there to help them breathe as I treated it. During the process, my red tailed shark vanished. I thought that odd since the night before he was swimming around as usual, fighting the current the filter made and having a blast in the bubbles. I assumed my catfish ate him. I checked in the filter, under the decor, outside the tank for the little guy. He was gone.
I later learned while reading that you shouldn't have the two sharks together, so I never replaced Alex (the red tail)
My filter quite working a month after the ich mess was taken care of and lo and behold Alex was in there! I checked in there with a flash light and didn't see him, so I must be half blind! I still feel so bad for the little guy! But he lived, is still alive, and seems to be fine. He has moved to a ten gallon temporary tank until I can get him a larger one, since I can't keep him and the rainbow together. He won't be staying there long, I promise. He is two inches right now at the most and living with a gourami, who is also temporarily in there.
Well the poor little shark has red gills and he scratches them once in a while. I know it's got to be from living in the filter for so long Sorry for the novel! I just wanted to let you guys know his story to help me know what is wrong with him. Besides the gills he is perfectly fine.
Thank you so much!!

 

[The Trooper]

What are the parameters of the temp tank? It could be ammonia burns.

 

[Krissycakes]

I am thinking he could be stressed. Oh or Ammonia burns. Or the water quality he is in. Sorry to hear about Alex. =( Do you have a test kit? How do you know if your tanks are cycled? Are the specifications right for both gourami and shark?

 

[Finian]

I use API testings for everything. I have the strips to test pH, hardness and so forth and then the liquid test kit for Ammonia. I'm actually buying the liquid pH tester too since I hear it is more accurate than strips.
The tank he is in now is ten gallons, at 78 degrees. The tank he was in was a 45 with a temp of 76, except for when I treated ich.
I tested for ammonia and it was fine, and we are doing 20 percent water changes every day to help keep it as clean as possible for him. Could that be the problem?

 

[Finian]

He has been in that tank for about a week now, too, if that helps. The tank has been running for over a month, as I got it when ich struck to move over some of the fish. Its been running without fish though for a while...