I have two 36"units on a six foot tank (or will when my tank is off the dining room floor and up and running). jrf what mods did you do?jrf said:I took mine apart in order to modify it. The plastic surface where the light diffusers are looks to be adequately sealed. However, where the plastic butts up to the edge of the housing isnÃ¢â‚¬â„¢t sealed tight enough to keep the water or evaporation out in my opinion. Personally, I wouldnÃ¢â‚¬â„¢t run mine over an open tank. Although, I must admit I tend to be overly cautious about this stuff.