The "right" direction for the water

Doug, if you pump your return water back into the tank (as opposed to gravity feed), swirling the water when it does, you should not need a drain for your fish tank. The solids will accumulate at the outgoing pump and be pumped to the grow beds.

Be sure your return water pipe into the fish tank is pointed in the right direction for your hemisphere. For you in Missouri, USA, NA, it should push the water counter-clockwise, or you will not get the solids to settle.

Paula

You are referring to the Coriolis effect When water or wind moves across the surface of the Earth, the Earth moves under it making it appear to curve to the right in the northern hemisphere. The whole picture is "clockwise in Northern hemisphere". The force applied by returning water to 1000 gallon tank would easily counter the coriolis effect if you sent it in backward. Try a sink. The slightest boost makes it spin in the direction of the boost. I'm going to stick with the plan in case direction matters for some other reason, but I thought you should know.

Uwe

You may be correct, Doug, that the water will "spin that way". How quickly it will spin I would guess would depend somewhat on the force of the water/power of the pump.

My comments were directed at the effect it has on solids removal. When we went against the Coriolis effect and had tanks circulating clockwise in the Northern Hemisphere, we had poor water quality due to the amount of suspended solids.

This was in no way a planned experiment. When we set up our tanks, we had four circulating counter-clockwise, and two clockwise. Trying to decipher why the two clockwise tanks would not clear up, then reversing the flow, is what caused us to remember that such a natural effect could also affect our man-made system.

Paula