I made one for a 75G with 1" PVC, tie wraps, and a light diffuser. All purchased at Home Depot.
I filled it with sand before I glued the end caps on. That gives it more weight than water fill.
I dropped it into the tank and buried the feet with gravel. No worry about big fish knocking it over. I was going to use suction cups, but after a while they loose their grip.
