How big is the clown trigger, that's the tell, really anything over 4" is a tale of 2 triggers. When purchased at a larger size the chances for a super aggressive clown trigger goes up. Starting with a smaller one and the chances of a good citizen goes up. Raising your own baby trigger, now you're talking. Clown triggers don't really grow that fast and don't end up being that large, will stay well below 10". Many times you will find other variables like too small of tank and inappropriate tankmates will lead to the negative reports. 300g is a nice tank for a clown trigger and they'll likely pay no mind to a zebra eel. This is one of those fish that may be ballistic towards any new comers, so considering it your last fish may be a good idea.