Are plecos usefull to the tank, or are they there for looks or personall preference. Because I've been watching videos on ponds for research because I soon will be getting one and there's one in every pond.
This is completely incorrect. My girl friend has 2 full grown 4" ish Clown Loaches and they add more bioload to the tank than any of the full grown angels and have the substrate covered in feces within 1-2 days of a wc. Plecos (large or small sub species) produce much more waste than they can clean in a tank as a scavenger and shouldn't be bought to "clean up tanks" which is a misconception that leads a lot of people to buying them only to hinder their tank cleanliness even more. I personally love plecos but gave my 9" common away to a fellow mfker once I experienced the giant bioload mess they bring with them. They look real cool but aren't worth the bioload IMO.