Bricks or blocks will hold, as long as they are stacked right. I prefer working with lumber, heavy screws, and plywood decking;
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That's a 3'x10' rack, above a couple of 150 gallon tubs. 2x6 lumber around the perimeter, 4x4 posts for legs, 2x4's for stringers. It holds five 40 gallon tanks & three 20 gallon tanks;
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This leaves plenty of room for plumbing underneath, as well as working room for the 150's;
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Always plan ahead for electrical & water requirements, the silver strip in the middle is all outlets;
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Make sure to leave working room between tanks, due to individual body structure this can vary. I'm 6", 225 pounds, and find that 50% of the tank depth, minus one inch is about the minimum I can leave between tanks & still have them reasonably workable.