Originally Posted by huma-huma
Why would you even buy a fish you can't house as an adult? You have to remember that a big part of this hobby is doing what's healthy for the fish. Sure as a juvenile the trigger would be content, but once he starts getting decent length to him its just gonna cause problems. Also what type of lionfish do you have? Volitan, fuzzy dwarf, radiata?
I see where you are coming from but I have my opinion on the matter and yours may differ. Larger species can be kept in reasonably sized aquariums for long periods of time. It's the aquarists duty to provide a suitable tank if it becomes larger. 1 tank move to a larger one won't hurt the fish, stress it yes, but let's face it fish get stressed very easily, after the move,it would be FINE, if we were truly looking out for the well being of the fish we wouldn't put them in tanks, and take them from their natural habitat. We just need to make sure it's going to a good tank. As we all know this can be a expensive hobby if your buying a fish to have for a couple of years in a tank, over those years a responsible hobbyist will be looking into buying a new tank.