I have had my laser for over a year and used it several times, no issues with the fish whatsoever. Like I said earlier, try after the lights go off. Also, be careful of the reflection of the beam on the OUTSIDE of the tank! It will reflect a very powerful beam that can blind and burn that way too. This is something that should be done alone with no lookie loos without eye protection.I think all the fish need to be removed or some kinda wall to block the beam reflection would have to be crafted. O well I got a sweet 130 dollar laser but wouldn't use it in aquarium with fish.
but who knew you could use a laser beam for vermetids. I have hundreds of these thing and would really like to know if it's worth it.

