Delhezi's can catch feeder fish, if they really want to. It took mine a little while to figure out what was going on, but once he caught on, he started gulping them down.
Well, I feed mine bloodworms and pellets, you could also feed them frozen beefheart, feeders, or any other kind of frozen food. You could also try freeze-dried food.
you can feed FD krill or market shrimp and soak it with kent marine FW vitamins , get some feeders that are healthy and gut load them with high quality food, or jus feed them floating/sinking pellets
Plecos do well in a species only tank, some fancy plecs have teeth and are aggressive towards other fish in their area.
55's and 75's are great headboards^
I would personally Opt to keep a fancy L#. I think I'm going to end up getting one for a species only 20L while I upgrade tanks!