Hmmmm. This is a hard one to answer.
Personally I wouldn't buy from a LFS who has poor maintenance on their systems. If you buy a coral, it's already been stressed out due to poor conditions.
1) so you're already starting in a
hole trying to heal a uncared for coral
2) you could be introducing microorganisms to your tank you cant even see with your own eyes as hitchhiker spores that can & will invade your tank. I introduced a coral 2yrs ago and I've now been fighting a majano outbreak ever since. It might take years for these spores to die off.
I suggest highly sought-after R2R Vendors who do Live Sales on R2R.
https://www.reef2reef.com/categories/sponsors.5/
To many of these Vendors, this is their livelihood and it's a requirement for them to have superbly clean growth tanks. They cant afford a nationally recognized BAD reputation of having corals arrive with hitchhikers. The US reefers would shame their biz into bankruptcy.
I almost exclusively buy from Vendors listed as Sponsors to R2R. Go and read the Vendor list. Read their online review posts.
Look for seasoned Vendors who have lots of discussion threads... a higher # than average
Unfortunately most small family owned LFSs doing OTC sales are starting to give up on the dying biz....
I certainly would not support a LFS with algae and Aiptasia filled reef tanks. Signs that the biz is quickly dying.....just like the corals they are selling
.