hI there I have a 50 gallon tank with some platys and bn plecos (hope to breed the plecos) my dad really wants a goldfish would it be a good idea or not? I’ve heard it’s not due to plecos attaching to goldfish because of their slime coat.
Unless the Platies are 3" or larger and you are going to move the bn's to a separate tank AND have room for 2 poop machines (goldfish are social, should be kept in at least pairs, in a large enough tank and group mine shoal and school a bit).
They will eat the baby plecos, plecos may kill them, they'll probably eat the platies, pleco spines can cause issues, and produce a ridiculous amount of nitrates. Not impossible, but IMO too risky, no need to put all the fish at risk.
I guess that would somewhat depend on the size of the goldfish and whether you plan to get a bigger tank later on for the goldfish as they grow.
Right now we have a 10 gal 2 feeder goldfish (about 1- 1.5 inches long, I plan to put them in my horses' water tank as soon as the weather is warm enough to kept algae down), 2 fantails (2.5 in ea or so) 3 corydoras, 2 mystery snails and my daughter just bought a trio of young platies with her Easter $ from grandma. It's a temporary situation, I am shopping around for a 20 to 29 gallon to move the fancy goldfish and 2 out of 3 corydoras (2 regular brownish ones and the other is albino, probably get 1 more reg and 2 more albinos). 10 gallon will become my daughter's livebearer tank plus snails. Bigger one will have the goldfish and the oldest son wants a smaller species pleco (he's a weird kid...I've given up asking why he wants one...last pleco I had was a regular one about 30 years ago and the thing was a menace, constantly breaking my heaters and such at 10 or 12 inches old. I sold him back to a fish store.)
I made my own filter for the tank I have now (huge for a measly 10 gallon) and it has a lot of flow and a lot of biological filtration, so my unconventional mix of fish is doing well for now. It's not a common community of fish, but it can be done (at least for a while...especially if the goldfish are pretty small ones and slower swimmers than the platies. I would start considering a 2nd tank though, eventually you will end up wanting to move the goldfish, if you want to keep the platy fry.