covering the tank

[Delphinus]

Why would you want to slow down evaporation? :confused: Evaporation is the best way for temperature stability. If evaporation is a problem, why not increase your top-off? A bucket, some air tubing, and a furnace humidifier float valve make a great topoff system for less than $20. I'm the king of cheap, I never wanted to spend a lot of money for a topoff solution... this method has been working for me for well over two years now. Not bad for $20.

As you might guess I'm on the "don't do it" side of the argument for your cover glass. Also, with a cover glass, you'll lose a LOT of light going through that glass at the BEST of times ... the way I look at it, I pay $20 per month per bulb to light my reef tanks, I darn well want as much of that $20 per month going INTO my tank and not getting reflected away or absorbed somewhere else before going into the tank. Again, king of cheap ... I don't want to spend money unnecessarily...