Feeder goldies are also known to be a bit unkept at a lot, if not most, shops: both LFS
and BigBox shops. I would keep a keen eye for any form of disease or problem and keep on top of it. Don't use any chemicals if you don't have to though.
I agree that you should have waited on the Molly. Sounds like you are indeed overstocked. Feeders can get up to 12", if not more. I've got a friend with about 6 in a Koi pond (1000+ gal
) and they range from 8" to 12".
As for temperature, goldies are a cold water fish, but can tolerate a mid-tropical water and aquarium salt. In fact, a standard treatment without "chemicals" for a goldie is to put in some aquarium salt (very small dose) and raise the temp slowly up to 78F. My fancy goldie is holding steady at 80F during a cycle with a small dose of aquarium salt.
So in regards to climate, you SHOULD
be alright as long as the feeders are already stable in a warmer environment. More than likely, most of your feeders will pass the cycle stress, if they are healthy. You snail should also do alright. You need to keep an eye on the Molly though for sure.