What size pump do I need?

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Aquarium Advice Freak
Aug 14, 2004
How do I calculate what size pump I need? I have a 75gal and will be using a Ocean clear 325.
How many GPH is the overflow rated for? How many feet of head will the pump have to return the water to the tank with?

Use these two items and then get a pump that pushes less water than your overflow can handle at the head height you have with your setup.
I'm not using an over flow. I unable to so I have to use hang-ons. That's way I'm using the 325 so I can lose the hangons. But to go from the 325 to the tank maybe 18in.
Searching the net has turned up the following information on that model of filter.

Use an external pump with a flow rate of 500-1600gph. Manufacturer recommends using a pump at the higher end, especially if using more than one unit in tandom. Inlet and outlet size is 3/4".
Or any other external pump that can do approx 1000-1500GPH at the specific head your returnning the water. The pump woudl go on the intake side of the filter unless manufactuer instructions say otherwise. The filter itself will introduce artifical head slowing the pump down more.

You wont want an overflow for this install instead a bulkhead below the water surface will be best to provide a constant intake of water that is free of air.
Do you mean I want an overflow? I'm a little confised on setting up and overflow in the tank? What would be good to use for the intake?
NO. You dont want an overflow with this type of canister filter. Overflows will introduce air into the plumbing and canister filter because of how they operate. The air will collect in the canister filter and evetually cause it to fail I suspect. As I said the best intake would be having a bulkhead drilled into the tank below the water surface so that a steady flow of water could be taken in via the pump and pushed thru the filter and returned back to the tank.
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