well, you have a lot of livebearing fish, and they like a good proportion of veggies in their diet, I would reccomend feeding them veggie flakes, which include a higher proportion of vegtable matter then your normal flakes. for the plecos, depending on the types, i'd say algae discs, but make sure you get one with a low proportion ofanimal matter, such as wardley. i've seen some "algae discs" that have more fish meal than actual algae.... (P.S. if your plecos are the normal ones, they will all outgrow your tank unless it is something like 300Gs, and I doubt that.)