Thank you for the replies,
I have gone over materials again, and am going to use 1/2" reduced to 3/8" tubing.
I will be using a spiral to avoid 90 degree bends (to prevent turbulent backpressure on the pump). Also two spirals will cover 90% of the bottom glass, and, with available materials, a grid pattern would only cover 72% of the bottom glass.
I am still struggling with size of holes, and how many. For testing I was going to use 12 1/16" holes on one closed loop spiral and see what happens. Depending on how the test goes, I may use the two opposing pumps idea.