One thing that I do is get a plastic clear medicine bottle from a pharmacy (they will usually give it to you for free), then I attached a rock with aquarium glue or a plastic tie to it so it will stay submerged. I will put an algae tablet in it and then put it in the aquarium. Make sure the bottle is just big enough for the fish you want to feed, but not big enough for the others to get in. Soon this will serve as a feeding station just for that fish. I had to do this trick when my bristlenose wasn't getting enough to eat, the pictus were eating everything so fast, nothing was left. This worked out really well because the pictus didn't even detect the feeding station. Once in a while a danio or barb would try and get in but my bristlenose was getting his fair share.
