Thanks Tristan. Most people say 300 gallons for 8 ft x 30" x 24" and 330-340 gallons for 9 ft x 30" x 24". These are not really very good approximations. This tank will have 3/4 inch glass on the sides and bottom and the dimensions are exterior dimensions. Taking this into account shows that the actual volume of this 9 foot tank is 298.9 gallons when filled to the top. It is 292.4 gallons when filled 1/2 inch from the top.
I have also made a change in my plans for the stand. The previous design is certainly strong enough to support the weight, but I started thinking about the wood flex and whether that would be ok for the glass or whether it would stress it too much. The previous tank stand design had a sag or deflection of .076 inches in the center of each half. I don't know any solid details on glass flex, but several web sites including
http://www.fnzas.org.nz/articles/techni ... _complete/
give a pretty good idea of how much glass can flex. Basically the answer is, not much. Ranges for safe flexing are .2 mm to 1 mm (and this of course depends on the length). The above .076 inches is 1.9 mm. This deflection is not counting the 3/4 inch plywood that will be glued on top. So it is possible that it would be ok, but I want to be very, very sure.
I could just use 2 x 6's on the top and all would be fine (the deflection is about 1/10 what it is with 2 x 4's). The problem with this is that I am not tall enough (5 ft 9"). Let me explain. I would like to be able to reach my arm over the side of the tank. With an tank stand interior usable height requirement of 24 inches so that my canister filters fit, using 2 x 6's does not allow me to reach over the side of the tank comfortably. Thus, I am willing to be a bit inefficient with wood just to make it easier to maintain later. If I use solid 2 x 4's on the top (20 instead of 8 ) the deflection drops to .026 inches or .66 mm. This is probably ok, but I computed how much room I need on one side of the stand for a reservoir and decided to cut the span on each side by 6 inches. This leaves 42 inch openings on each side and a small 10 inch wide opening in the center (which I can put shelves in for small items). The deflection in this case is .009 inches or .23 mm. So this is the current plan (despite my sister-in-law's advice of: Just use 2x6's and get a stool). The diagram is below.
I bought the wood yesterday, and I got a lot of comments from people as I loaded thirty-eight, ten foot 2x4's into my Prius. Comments like: "Are you going to put all of that in there?" and "You should make a commercial, Prius as a pick-up truck".
