approx. cost for a plywood tank????

Given the varing costs of plywood, and glass in your local area the best thing to do would be to visit your local Home Depot or equivlent Home improvment store and check out the prices on the lumber and glass.

I priced a tank out simular in size once and I came to the conclusion it would be less than $250.
 
Plus add in cost of any silicone you will be using as well as any epoxy paint you might use. The paint alone can add close to $100 depending on where you get it.
 
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