Crap, meant to say sharks, not catfish (even though they are all actually catfish). I thought the red-tail would get to by 4 inches (6 at most) and still be okay for the tank. I've only had him for several weeks but he's been doing great. The other two have been in the tank for years and each have their own section of my main decoration and even though they keep getting larger they always have seemed to do really well. I hope at the end of the year to use them to help start a new larger tank (probably 75-100 gal).
As for the Barbs, I have 2 tigers, 1 green tiger, 1 electric glo tiger, 1 panda and 1 gold. They all school together (except the glo who is brand new) and have always seemed to not cause any issues for each other. My end goal with this tank is to have a barb tank showing off some of the favorite species I've seen. I hope it's not unrealistic, but so far every new barb has gotten along with those there.