Down pipe and return pipe sizes for a custom 120cm x 60cm x 60cm aquarium

6 May 2007
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Vredehoek, Cape Town

I am considering going the custom aquarium route and are trying to figure out pipe sizes. I may have over-designing things in the past on my previos tanks.

The tank will be more or less the same size as a Red Sea Reefer 425XL. I am planning to have a full bean animal overflow (two operational down pipes, one emergency drain) and two separate returns (and pumps) for the tank. See the drawing.

I was thinking of scaling down to 20cm diameter pipes for both the down pipes and the returns. It would make life so much easier, takes less space, cheaper fittings, valves, etc.

Is this big enough? How much flow would I be able to push through the two up/down pipes assuming a reasonable amounts of elbows?

Looking at the RSR pipes, they look even smaller with a single operational down and return pipe.

Also, what sizes are Apex/GLA flowmeters available in?

Screenshot 2020-07-30 at 21.41.11.png
28 Apr 2015
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East Rand
I had an 4ft with 4x 20mm outlet and the best I could get was 2000lh . The biggest problem is the tank connector lowers the 20mm hole to an 15mm.
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