I wanted to resurrect this thread and add another issue that is bothering me about my rimless tank. I am running two 1/2" sea swirls on a mag 950 for circulation in a 58G Illuminata tank. This pushes my flow up to about the maximum for this size of tank with a constant sandstorm. In my old tank, this setup worked great because when the sea swirl was pointed directly at the front glass, the trim would knock the flow back into the aquarium. Without a rim, any flow that is strong enough to climb near the top of the rim will cause puddles on the top of the rim and eventually drip down the sides. Basically, a rimless tank has lower flow capability than a tank with trim, unless you want to clean up a mess all the time.