Another "how big should my sump be" question

[indy]

Here's my 55's fuge. The water line you see is about as full as I myself will fill it. One of the bonus features of this design is built in display tank flood protection. If you look in the far right chamber you'll see my return pump. The chamber is comletely sealed with silicone from the rest of the 'fuge. In the event my overflow siphon breaks, my pump can only return the contents of that chamber up to the top of the baffle. In this case, it can only pump 1 gallon of water into the tank before the pump runs dry. If I pull more than 1 gallon out of the system the pump starts sucking air, and won't pump in more water until the siphon is started again. I keep the display about 3/4" below full so it can absorb that 1 gallon flood with no problems. The closed loop using a hob overflow prevents the fuge from backflooding if the pump fails. I keep my return line right at water level, so in a power failure it only backfills about 1.5 gallons which is easily absorbed by the fuge. You have to trial and error to get the adjustments right, but after that you don't have to mess with it. Having a quick finger on the power button is a must

Tyger: I have a 6 inch sandbed in the display tank and a 2-3 inch sandbed in the center compartment of the fuge. There is also a large hollow rock inside all that algae. I also keep about a half dozen snails living in there to keep the substrate stirred. Poor little fellas are nocturnal by nature, but live in 24/7 light. They seem to have adapted well to it tho'

http://www.aquariumadvice.com/photopost/showphoto.php?photo=4889&password=&sort=1&cat=500&page=1

Ok, I give up. Stupid picture posting %*$%*^^%)& never works for me for some reason.

 

[TygGer]

I've only seen a few different sump/fuge designs, but yours seem to be different than the norm. In my design, I'll need to add enough space for the skimmer.

I have a built-in overflow on my tank. If I'm understanding correctly, the water level in the display will remain constant no matter how much water I add to the sump?

If this is true, then does anyone know approx how many gallons drain into the sump if the return pump failed?

Let me try this...

 

[TygGer]

To post a pic...

Go to your pic and find out the location. You can right click on the image. You had the right idea, but you tried attaching a link to the image (page location), instead of the image itself.

You needed:
http://www.aquariumadvice.com/photopost/data/542/5654DCP00871-med.JPG

 

[indy]

I guess thats what i get when I'm typing when I should be sleeping. I did my design for my specific purpose. Since its only a 10g there was no room for a skimmer, so I didn't have to work around it. The tank I'm working on now will have a much larger fuge, but the same basic design. The only difference is an enlarged pump compartment so I can drop a skimmer in with it.

As for the overflow, as long as your overflow can pull more water than your pump can push, it will always stay the same level in your display. You change the level in the sump by raising or lowering the overflow height. The amount of water it will draw in a pump failure depends on your display tank size, and how deep you have your overflow mounted.