| You won't need a gate valve to fine tune your flow, and here's why:
Your tank is only going to drain so low, correct? When it gets to that "low" point, it stops draining.
Now, otoh, your pump is returning a constant velocity, correct? This means that your tank water is going to drain however fast you return it to the tank. Any 3/4" -1" drain will handle a 330 PGH drain. The important thing is just to make sure your drain is LARGE enough to handle the return. It's not going to drain any faster than your pump gives it back to the aquarium, as the water will just flow back down before raising tank water height.
Confusing, but hopefully that made a little bit of sense?
Cos |