i dont want to sound like i dont know what im doing cause sometimes i like to pretend i do but why do you say i shouldn't have the pleco with the bichir?
like somebody already answered they have a tendancy to latch on to the bichirs and suck the slime coat which essentially strips the fish of it's immune system and leaves it open to diseases and what-not
You might want to try more greens in some of your fishes diets this might help with them eating your plants. Or get a moss ball or something like that were you wouldn't mind then eating it. My plecos stripped my swords down to stims in a rather short period of time.