Posted: Sat Mar 24, 2007 7:50 pm
I learned it from the reefkeeping hobby. A lot of us like to keep deep sand beds along with reef rock. They can add up to an additional 200 lbs on top of the bottom glass. With this kind of weight (along with the 9lbs/gal of sea water - heavier than fresh water) it is extremely important to make sure that the surface the tank frame is resting on is perfectly flat. Variances as little as 1/8th of an inch can cause enough stress on the tank to cause it to give out over time. Enough people have had large tanks (100 to 300 gals) empty out on their living room floors after several years without problems. So a lot of brainstorming went into how to prevent such disasters as much as possible. One idea was using a soft foam pad under the tank frame to smooth out any irregularities in the stands surface. That idea was carried a step further by using a little extra foam under the glass portion, but not too much. You want the tank resting primarily on its frame as it was designed to. Just a little pressure under the glass can help alleviate some of the stress from the heavy weight of the rock and sand. It also provides extra insulation. That's what's fun about reefkeeping, there is a lot of science, physics, biology, mechanics, plumbing, electrical, carpentry, etc. involved. Keeps it very interesting.
