Backyard Aquaponics
A place to discuss aquaponics

Not quite... You need to allow for head loss and friction loss. You need a pump that would flow at least 400Lph at the height it's required to pump up to (the head), and taking into account friction loss in the piping as well. The longer the horizontal runs of piping are, or the more elbows and tees etc in the plumbing, the more loss of flow there will be due to friction loss.

For example, say you had to pump the water up 1m and you had very little in the way of horizontal runs, elbows, tees etc, you'd most likely look for a pump that would flow at least 500Lph, possibly even 600Lph at 1m head. It may turn out the pump needed to do that is actually an 800Lph pump.

If there was extensive plumbing, ie long horizontal runs, quite a few elbows, tees etc, then you'd need to look for a pump that flows even more at that same 1m height, maybe a 1000Lph pump would be required.

There is usually a flow chart on the side of the pump boxes which show their flow rates at different head heights.

I like to oversize the pump by at least about 30% (even as much as 50%) over and above the minimum flow rate I estimated that I need. Any excess flow can always be diverted to a spray to help with aeration of the water.

I am planning to get a 600 for my 400 system but since I have to pump it directly upwards at 3 mtrs high I might get an 800 depending on the kind of pump. rotary has little slippage compare to centrifugal.

Have a really good look at each pumps flow chart before you buy... I don't know of any 600Lph pumps that will even pump to 3m, most stop pumping completely at around 1.5m to 1.8m

yea most;y small pumps dont pump that height. Thanks