The tank looks cool so far. Here are my thoughts:
1. Is the tube in the middle a supply line from the sump? If so, is it going to have something to prevent it from draining water back into the sump if the pump shuts off?
2. Do you think there will be enough flow throughout the tank with all the supply lines running so close to the overflow? You could maybe add 45* PVC elbows to the ends of the pipes on the sides to help circulate the water.
That's about all I can think of.
If this tank turns out half as cool as your little cubes did, you'll be laughing.
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LovelyWendie99