A very interesting topic, as I have had similar questions.
I have a few broods of cory fry due to be shipped of to the LPS any minute now and I've been thinking if they give me store credit instead of actual money I'l be very tempted to fill the void with creatures, and about the top 2 species on my list at the moment are coolie loaches and hatchet fish. Most of my "mystery" snails live in the big comunity also, so I do need to check on some compatibility issues. i thought I had been told that coolies would help control the pond snail overpopulation, which I want, but I also have apple (mystery) snails posting eggs on the ceiling. I doubt the loaches would know the difference. I used a breeding box when Momma snelly lived with goldfish and they ate the babies. would I need to do that for my comunity too. the ones that hatched a few months ago are doing well, but I did move about half of them in with baby cories for a while because they grew faster that way. Now they are almost as big as my LPS wants them, but the variation in size is amazzing considering they all hatched at the same time. If I just sell the big ones, am I likely to be loosing mostly 1 gender or all the healthy ones or something? Oops probably getting off topic.
umm, so if i do put coolies in my comunity, do I need to move baby apple snails?, if so up to what size? maybe they'l go back to the guppy breeding tanks again.