My first ever tank was a 29 show. I didn't know what the hell I was doing, and unfortunately nobody at the LFS discouraged me when I bought a bala shark, a blackfin shark, 3 clown loaches, and exodon, a small eel, a lime shovelnose cat, a couple of barbs of some sort and 2 oscars for it (not that it's their responsibillity, I should have done a little research). As you can imagine once the fish started growing at all the bio load got crazy. I went out of town one weekend and came home to find everything but the bigger oscar and 2 of the loaches belly up. One of the 2 loaches died soon after, and I kept the single Oscar and the other loach for a couple of years after that. The oscar got to about 10 or 11 inches and mean as hell. He would bite your finger if you tapped the water. I fed him fish food, but whenever I had the chance I would feed him june bugs, crickets, feeder fish, small crawfish and my favorite "prey" to feed him was big green anole lizards. He would hit them head first and swim around with their rear feet and tail sticking out of his mouth for a while.
When I eventually moved I gave the oscar away and tore the tank down for a while. After a while I set it up with an appropriate number of smaller tropicals and ran it until hurricane Rita Hit. I was without power for 21 days after the hurricane so I lost most of my stock. I had to gut and repair my house and no way was I going to have room or time to maintain an aquarium so I finally sold the old 29.
I'm just setting back up with a 75 gallon and plan to do natives. I'm taking my time setting up, tank is up and filled, but I probably won't stock it until late March. This time I'm making sure everything in the tank has enough room and the right conditions to thrive.