if you are adding baffles to an existing glass tank, you have three options:

1. glass baffles - they must be cut nearly perfectly and the glass bonds very well with silicone

2. acrylic baffles - not as critical on the cut, actually a hair too big works better so there is a SLIGHT bend on the baffle that keeps VERY SLIGHT pressure on the sides since acrylic doesnt bond as well with silicone. also, rough up the area of the baffle where it needs to bond to the silicone.

3. pressure lock baffles(link)