Welcome to R2R! When I've been choosing fish for my tank, I first look to see if the tank I have matches the recommended tank size for that type of fish. Then I look at the aggression level, based on the consensus you should add the more peaceful fish first, and in an effort to ensure there are no known breed compatibility issues. Lastly I research the problems people have had with the fish in the past. Looking up how to remove a type of fish from a tank is a good way to find the "cons" of any fish.
Welcome. I to would encourage you to slow on the introduction of more live stock to let your system balance. Your bacteria uses the ammonia/ nitrite — nitrate. If you intro more that produces these you could get a spike witch can really stress out even kill your fish. Best to be safe. Will have to check out the high fin. Not seen one. Have a pink barred goby should be here tomorrow for my pistol shrimp.