It is a calculated risk for sure, The main thing that is concerning me is the fact that I don't know this fish and how it would behave outside of the 40g in the lfs if I had raised it myself I think I would be more keen on trying it. With my luck he will feel all comfy and at home in the 300 after a week or two and start snacking on everything. I may still try a mbu some day but I am pretty sure I won't chance this one