While its not something I will encourage, I kept a group of 6 tiger barbs with my angel in a 55 for about a year and a half with no problems, at which point I lost all the barbs in a tank crash.
The shark catfish is probably a Columbian shark, and they do need brackish as they get older. See profile: http://badmanstropicalfish.com/profiles/profile63.html
OP - original poster (you, crashlee).
I'm not sure what tank your oscar is in, I'm guessing the 100, but IMO thats not really big enough to house a full grown school of bala sharks. Are very active and get large, and really deserve the proper space.
Other than the space issues you are bound to run into, the ram should be fine in that tank for the time being. Just make sure you keep up on water changes - that is a fairly heavy bioload for a 55. I'd be doing 50% weekly, bare minimum.
The shark catfish is probably a Columbian shark, and they do need brackish as they get older. See profile: http://badmanstropicalfish.com/profiles/profile63.html
OP - original poster (you, crashlee).
I'm not sure what tank your oscar is in, I'm guessing the 100, but IMO thats not really big enough to house a full grown school of bala sharks. Are very active and get large, and really deserve the proper space.
Other than the space issues you are bound to run into, the ram should be fine in that tank for the time being. Just make sure you keep up on water changes - that is a fairly heavy bioload for a 55. I'd be doing 50% weekly, bare minimum.