I currently have one snowball pleco, he's 2 inches and I'm wondering if I can get any more plecos or will they not do well together? Plecos are the most fascinating freshwater fish to me, they're fun to watch.
You could fit one other pleco. I keep a clown pleco and a bristlenose in my 55 gallon harmoniously. The biggest issue with keeping most plecos together is usually the amount of waste they produce rather than territorial aggression. Just be ready to do a lot of vacuuming on the floor of your tank to clean up after them and it should be fine.