Hi, Amy --
I haven't read through the replies, but did read your oginal post.
Obviously, I'm a horse person... but I'm also pretty much an avid fishkeeper!
With plecos, the common (brown) variety, I think, I very territorial. So you wouldn't want more than one in a tank. Plus, they also do create a lot of waste and, if they live long enough, become very large. They are most often kept in "tropical" tanks, but actually can do well in household unheated goldfish tanks. But, I don't think they could ever do as well as goldfish when it comes to a wide range of temperatures. Additionally, they are very noctournal and should have a log, driftwood (ideal) or at least a PVC pipe to hide in during the day. We have quite a few... two common in large tanks (one in a big goldfish tank, one in a tropical type tank) and lots of neat "bushy nose / bristlenose" albino plecos that are not so territoral.
Our horse tanks here are just those low 55g Rubbermaid kind. We don't keep any fish in them. I just have a toilet brush (obviously, not used ever in a toilet!) and periodically scrub the tanks with that. It only takes me a couple minutes per tank
Best of luck!!!