Difference between sump and refuge?

[Kyle C.]

I'm in the planning stages of a 75 gal marine tank and some one suggested I use a sump. Is a sump and refuge the same thing or is it a different piece of equipment all together? I believe the reason for using one is to increase the water volume on the main tank to increase the water stability. I have a 30 gal that should fit under the 75 gal stand, but I never used one before and am a little scared of pumping water under the main tank, how do you keep all your water from running on the floor if the power goes out to your pumps? Sorry for such a noob question, but thanks for any help on the subject.

[hursab]

Usually in a sump you put equipment like heaters skimmer etc. more water more gas exchange.
In the refugium you grow alleges and put live rock to have beneficial bacteria and also adds a few gallons but not much.

As for the plumbing there are a few options like an extraction box or drilling a whole in the tank as high as possible. In both cases if the water lever goes below a certain level the plumbing cannot siphon any more out. Of course you would leave a few safety inches in the tank below.

[Kyle C.]

Ah ok, so you use a sump to hide your equipment so the display tank has a cleaner look and a refuge grows bacteria and maybe small critters as a food source. Thanks for clearing that up for me.

[aspects]

The sumo is essentially the tank (or other container) that sits under your display tank. basically the whole thing is the "sump".
The "refugium" is a section within your sump. This section holds things like live sand, live rock, chaeto, and things like that which will aid in biological filtration.
Your sump would also have a section that houses your protein skimmer, heater, chiller, or NY other equipment you want to keep out of the display. And a section that houses your return pump.

Generally you want a sump roughly 1/4-1/3 the size of your display. This way, when you turn the sump off (or in the case of a power failure) your sump will be able to hold the water that backfills into it. Usually your overflow (drilled, PVC, or skimmer box) sits just under the waterline, so the backfill will only be a few gallons.