possible tankmates

Question
I currently have 1 yellow bellied slider, 2 channel catfish, 1 pleco- (not sure the exact species but it's very common to most fish stores) as well as 1 red tailed barb. And I was wondering what kind of fish can I add to the tank considering I have a 150 gallon tank and I was thinking about a florida gar, striped gar, or maybe a North American cichlid. I am also willing to get rid of the red tailed... considering my pond turtle ate the last one... for some reason this one is still alive

Answer
Hi Philip,
The catfish and slider both hunt little fish, as long as the fish are big and semi-aggressive or agressive you shouldnt have a problem.  The turle might however bite the pleco's tail.  I used to keep a red-eared slider with a pleco and the tail kept getting bitten off, it would eventually regrow back over and over.  The cichlids will be fine but if they are bought small, both the catfish and turtle will prey on them.  Remember that the catfish and turtle have a very large bioload so remember to do water changes even in ponds to reduce nitrates.  
-Matt-