my clowns used to host my open brain. The brain did great, didnt care at all. But since the clownfish nussled up against it at night, they did have some black spots on them from stings. But these stings were just concentration of melinin and didnt hurt the clowns at all that i could see. However, they have since moved. I had some macro that envaded the space of the brain and they had switched to that. more cover. As the macro grew along my tank, the clowns followed it, stopping at a patch of anthillia once i removed most of the macro. They now love it there, but the male seems to spend more time there than the female.