OK I know you should not have common plecostomus with Goldfish but I have seen allot of tanks that have them and and I was wondering whether they keep the pleco in coldwater temps or they heat the tank and keep the goldfish in a tropical tank?
I have seen it done before... any fish will adapt if they are hardy... but it is not recommended. Sorry, but 2 goldfish in a 15 gallon is stocked. I wouldn't put anything else in there.But, if your willing to do water changes frequently to keep them happy, I can't see why you cant get a pleco (just make sure it is a smaller species such as a bristlenose)
Sorry for sounding rude but I couldn't make it sound less rude...
You are correct that tropical fish should not be mixed with temperate fish such as Goldfish. However, I know some members do have Goldies and Plecos in outdoor ponds and they do very well.
Keep in mind that both species are large waste producers and require larger tanks. For Goldfish it's suggested the 1st Goldie have 20 gallon's and 10 gallon's for each additional Goldie. Some plecos can grow to 18" and even larger.
Plecos need tropical temperatures of no less than 73 degrees. Gold fish like cooler waters but should do ok in the lower 70's range.
I'm sure you'll get more responses.
Best of luck!
I've moved your thread to the Aquarium Stocking Questions section of the forum.
you could get away with doing that, but as ken said, they both produce a lot of waste... have you considered these https://www.fishlore.com/Profiles-WhiteClouds.htm ? the photos on that page don't really do them justice... You just have to see them (very active!). If I were to get a coldwater aquarium smaller than 10 gallons i'd have them!