Originally Posted by Hypnox

Good point with the trigger. Likely it would eat any invertabrates that got put in there. I would suggest doing very thurough weekly cleanings to try and vacuum up any detritus left behind. The lion and trigger are both very messy eaters. It should also be noted that as the lionfish gets older and larger it may start looking to your damsels and clowns as a food source.

I've looked at your aquarium info posted and notice you have extremely high ammonia and nitrates listed. These could be brought down some through the use of a protein skimmer, you say there isn't one on the system. With fish that are as dirty a bunch of eaters as large triggers and lionfish are a skimmer would help maintain water quality.