yeah some plecos end up likeing the taste of other fishes slim big plecos over a foot can take scales off or cut the skin of scale less fish like catfish little ones will just eat the slime which can stress fish out and leave them suseptible to bacteria infection its not as big of a problem with these kinds of fish RTC lima shovelnose and tiger shovel nose will shed there slim coats often but plecos can still cause problems for them better to remove the pleco