I would never trust a Trigger with any kind of slow or stationary fish like a Blenny. Triggers and Puffers are very well known for tasting fish to death. I am almost sure this would happen especially with the Undulated. I wouldn't worry so much about the Niger. They generally tend to be pussy's. I have a pair in my 209 and it is so cute because they always hang out together. They don't bother anything else except for making sure the other Triggers are kept in check (White tail and Rectangular Huma). It is just a matter of time before the triggers kill all the snails if you decide to get them. Pretty much no invert is safe with a Trigger. I used to have a red Hermit in the 209 but have not seen it in about a month or so, so I think the triggers got it. As far as keeping an Undulated with other fish, I used to have my boy with a Niger Trigger, 3 Silver Scats, Arthron Puffer, and 2 Volitans Lions. It worked fine. Then I set up the 209 and most of the fish got moved to the 209 while I moved the Undulated (now approaching 4 inches!) to the 46G with 4 Bar Gobies. Everybody gets along great... for the meanwhile anyway. Undulateds have totally different personlities but as babies they are generally pretty laid back. As they grow they can get pretty nasty. This is true with all triggers. Undulateds and Queens are by far the most unpredictable. If an Undulated blows a fuse, you will have no more fish tankmates. And this can happen overnight. I have heard of people going to bed with the tank fine and waking up to only an Undulated Trigger with the corpses scattered over the tank! Just to warn ya. He should be fine for now but watch him in the future.
