I bought these single polyps and was weary that my fishes will nibble or they would come off the plug. Any issues with trying to grow these on a mushroom cage until they start having additional polyps?
They'll be fine in the cages as long as they're getting light.
But that's also a very good reason why I always buy a cluster and never a single polyp: If something goes wrong with the original polyp, you have backup. Especially if it's an expensive named Zoa.
Now if you just got a bunch of single polyps for a buck or two each, you can probably afford a failure or two.