in my 55 gal i have an albino oscar and 2 plecos (small, like 4 in) ands a 6 in chinese algae eater... Ivory (My oscar) picked on em, cuz they ran, but then she started to leave them alone...I thought plecos were scary at one time and was told the need lots and lots of room... When I got my first tank i got the smallest pleco i could find...she is now over 2 and a half and is still in my 20 gal comunity tank, happy as can be...but the 2 in my 55 gal are getting big...they like to play (seriously...) they will chase one another and then relax and "cuddle" and sleep together...I now love plecos...