spiral_72 wrote:

Quick question, (I hope)

I have a 300gph powerhead, made by Aquaclear I think. It really moves a
large volume of water if I just drop it in the water. I decided to
build a canister filter underneath my tank. I bought some 1/2" flexable
clear tubing to move the water. By just adding 4 foot of tubing to the
pump, flow drops significantly. It won't even pump water from a tub on
the floor into the top of my tank. If I restrict the flow at all, the
pump chokes. Much to my suprise, this pump ain't gonna work. What
should I use for a 55g?

my aquarium page, info and pics at:
www.geocities.com/spiral_72/Spirals_page.html


Are you building a canister filter, or a sump filter?

A canister filter is typically a sealed unit, and a closed
system. The pump doesn't have to lift the water, only circulate
it. The only flow losses are from tubing friction and fittings
(and eventually dirty filter media). A better test for this
situation would be to put 8ft of tubing on the pump. Put the pump
in the tank. Bring the tubing out of the tank, loop it down to
the floor and back up with the end back into the tank. See how
much water you get out of the end. This will be in the ballpark
of the flow you would get with a canister spliced in at the
bottom of the loop (very lightly packed with new media), no nasty
fittings. 3/4 inch ID tubing might improve the flow slightly.

On the other hand, a sump filter is an open system. And the
water has to be lifted by the pump from sump back to the tank.
The amount of lift, in feet, that the pump must overcome is
measured vertically from the water level line of the sump to the
the water level line of the tank (for most common arrangements).
you also have to consider that tubing friction loss, and losses
for fittings and elbows can easily add another foot of head or
more.

Like Jim suggested, The Mag 5 is a nice pump. I use this pump
on my sump filter for my 75 gal, maximally stocked tank.

Bellow are the performance numbers for the mag 5 pump. It is a
500 GPH rated pump, but you can see how quickly the numbers fall
off once a little head is added.
I minimized the tubing and fitting losses in my setup, by using
over sized tubing (1 inch ID smooth bore spiral wound) from a
pond center, and by using NO elbows or fittings, except for a 1
inch OD long-sweep "J" bend to get over the top of the tank.
Lifting a little over three feet, I'm guessing I'm getting
somewhere between 310 and 340 gph.

Mag 5 Pump Performance
@ 0' 500 GPH
@ 1' 450 GPH
@ 2' 415 GPH
@ 3' 380 GPH
@ 4' 310 GPH
@ 5' 250 GPH
@ 6' 180 GPH
@ 7' 125 GPH
@ 8' 80 GPH
@ 9' 45 GPH
@ 10' 20 GPH

http://www.pondliner.com/PondmasterPumps.htm
Is where I got the above table. Go there, then click on the pump
model numbers to see characteristics for the different sized
pumps. This page is one of a good hand full that show pump
characteristics.

Note; Characteristics are different for each brand, model and
size of pump, so the charts aren't transferable.

I hope I've got this all right.
Good luck on your project.
Paul