Attached is a little diagram of my setup.
The tank is a glass paludarium, if that helps explain the placement of the overflow. The water level is very important--too high and the water drains into the land portion of the tank, too low and the fish don't have enough room to swim about.
Tank to Overflow siphon (1/2" pvc): The output end is in a little container that I can adjust up and down to adjust the water level in the tank. A strainer is placed on the input end (a piece of pvc with holes drilled in it capped with a cap with slices cut into it).
Overflow to sump drain (3/4" tubing): The intake end is kinda setup as a durso standpipe (except that it drains to the side rather than straight down). The output is above the water in the sump. When the new pump is in operation, the drain makes a horrible gurgling noise and periodically "sucks" all the water out of the overflow (its weird--suck...stop...suck...stop...etc) Leads me to believe that my tank to overflow siphon can't keep up.
Return A (1/3" tubing): A small pump (AquariumSystems Mini-Jet 606) supplies a waterfall. No need for a check valve. The pump is operating at about a 3' head (max is ~4'). Max flow is given as 82-153 gph, so I approximate the flow rate to be about 82-100 gph. The pump is a little old, so I'm approximating on the low side. I'm approximating because I can't find a flow vs height chart.
Return B (1/2" tubing--not shown in diagram): The new pump (Rainbow Lifegard Quiet-One 3000
) supplies a stream in the tank. This one has a check valve. Quite frankly, I have no idea what I was thinking when I purchased this model. At a 5' head it delivers 500 gph. I'm not sure what the true head is--3' height, about 7' in tubing/piping, 4 pvc elbows, and a pvc cap (full of small drill holes) at its end. The link provided has a flow vs head chart.
So that, in a nutshell (coconut?), is my setup. I'm really kicking myself for not getting an acrylic tank and not thinking of a sump setup beforehand. This is/was my first project, so I didn't even know sumps existed when I started the thing...oh well.
Any help would be appreciated! I'm planning a trip to the hardware store, time permitting. The tank is currently running with the setup shown...but only the waterfall pump is operational.