Polys and plecos

[Cohazard]

There's so many variables into why this could turn into a problem in your aquarium or not.

If all the fish are well fed, you most likely wont have any issues.

If the plecs go hungry or aren't being catered to enough, they will turn to slime coat because the bichirs are bottom dwellers mostly and easily picked on.

 

[Infblue]

and to add to killerfish's list, gars can also be targeted. so its not just bichirs. and ropefish are also in danger too. but they are a lot thinner and may be harder to get a good grasp on for larger pleco, so they are probably in less danger than say an ornate.