I will be adding a sargassum trigger to my tank this weekend so I'll let you know how safe he really is.

I've had several at the store over the past year and they have all done very well. They are not a fast seller they have usually been in the store for a pretty long time, in fact the last one I had was in a 20 gallon for 3 months before he sold and was doing extremely well. A very shy fish few the first few weeks but they have always become bold and personable after some time. Well that's my experience with them so far, I kinda think of sargassums as a crosshatch trigger minus $200 worth of color.