[trashion]

You should first ID the plecos and figure out what kind they are. If it's a common plecostomus (see here: http://www.aquahobby.com/gallery/img...costomus_2.jpg) then all 4 need to go back. You don't need an algae-eating fish. If you don't overstock the tank and keep up regular weekly water changes, and don't leave the light on too long-you shouldn't have more than a normal dusting of algae.

If you get a spiny eel, make sure you get either a Zig-Zag or Peac0ck eel. A Tiretrack will get too large, as will a Fire eel.

I'd recommend picking up more Tiger Barbs as well to give them a good-sized school.