Just reading you signature right now...I think we have a few more issues then the convicts right now...
The clown pleco will be alright in the 30gal, but the common pleco will grow much too large for that tank. Secondly, the African cichlids should not be mixed with any of the other fish in that tank, and they get to large for a 30gal, and should be kept in groups with lots of rockwork etc. The pair of convict cichlids will also become far to agressive for that tank, and potentially harm the other fish in the tank. Jack dempsey grows too large and should also not be mixed with any of the fish in that tank...Texas also grows far too large, along with the eels...