Salt Water ponds

[three90s&125sump]

A 50 gallon garbage can with a float valve in it to "flush" all the water out of it at the same time.

[pactrop]

actually you can do it without the float switch. The Waikiki aquarium invented one where you have a pump fill up the barrel above the tank and there is a large pipe starting just above the bottom inside of the barrel with a bulkhead near the top, going back to the tank. so when the pump fills the barrel past the top of the pipe it starts a siphon to drain the barrel like a wave surging into the tank. I think you can google the design. I believe it was Bruce carlson who came up with it.