Do you just want them stacked vertically on top of each other? That's like an hour worth of work and ~$20 in lumber. With 20 gallons you don't need to worry about shearing.
Thanks for the great link. I guess I'm a bit intimidated, which I shouldn't be, but my experience building something with wood is pretty much limited to a bird house as a kid.
Wouldn't be hard to do yourself, all you need is a drill. Home Depot will cut the wood for you, $20-30 tops with the cost of lumber. Just plan it out simple and assemble
When do you need this build by? I am building a new stand for my 250 gallon to match the 300 gallon. If your fine with that design pick up some lumber and we can build yours at the same time.