Some people (actually, just Kris) have asked me to go into a bit more detail about the whole sump idea.  I goes like this: marine animals are much more sensitive to changes to their environment.  This includes temperature, salinity (which changes because of evaporation), and other impurities (which they don't like at all).  In the wild, the ocean acts as a huge buffer, and these changes take place over years, if at all.  Home aquariums don't have luxury of vast amounts of extra water waiting to be used.  The people who keep the aquariums have two choices: 1) frequent water changes every 2-4 weeks and pray nothing goes wrong in between, or 2) and an extra source of water to dilute and lesson the impact of and changes AND water changes every month.  

I started my tank with choice one and stuff went wrong.  Corals died messing up the tank causing me do more frequent water changes (salt isn't exactly cheap ya know).  Even with the frequent water changes I couldn't keep up with the problems.  Then their was algae.  Ugly hair algae that almost killed all the corals.  So I convinced the wife we needed a sump NOW.  Putting one in the tank stand was out of the question because of lack of space under there.  That and I wanted a SUMP, not one that holds a mere 5 gallons.  I wanted the ability to double the capacity of water if needed.  So I got an empty plastic 55 gallon drum from a contractor I was working with.  The drum was used to store perfume agents for landfills and I couldn't get rid of the smell.  It was probably just in the HDPE, but I didn't want to take the chance, so I put the largest garbage bag I could find and duct taped it to the drum.

Our tank it in a corner of the house, which when you go into the basement just happens to be the same corner as the sump pump.  This would work out great just is case anything really bad ever happened and the entire tank drained in the basement. Instant clean up.  Now for parts.  To get the water to the basement is easy: start a siphon and let gravity do its thing.  Getting the water from the basement to the tank is also easy: a big pump (14 feet of head to deal with).  The hard part is keeping the water in the tank AND keep the siphon if the power went out.  Another note here is that most straight siphons will out do the pumps easily (at least in my case).  What to do?  They happen to make this great device called an overflow box.  The box is designed to only remove the water that is ADDED to the tank.  And never lose its siphon if the power goes out.  And not drain the tank to the bottom of the intake.  The science is easy if you look at a picture:

The smaller box with the cuts in it at the top is what site in the tank.  The rest sits on the back of the tank.  Works great once you get the siphon started in the u tube.  What a pain in the ass that is!  The overflow I bought is rated at 600 gallons per hour, so unless I plan on moving up closer to the tank, I'll be more then OK.

The picture below show the basic setup.  The white PVC pipe you can see in the upper right hand side is the return tube.  This drains into a 4"  corrugated PVC drain pipe.  Light, cheap, and works better then solid PVC pipe.  The filter is as fallows: 1) filter floss - to catch any big particles that may be in the line 2) Plastic window screen to hold the floss in place.  This is where the corrugated is better.  If you look really close, you can see white bands around the black tube.  These are the plastic zip ties that are almost unbreakable (more importantly rust proof!).  The reason the corrugated is better then solid PVC is the instead of using super glue to hold the screens is place, I can just use and zip ties in the ridges and not worry about getting the super glue all over my hands (that really sucks).  3) Next is the Bio-Balls.  About the size of golf balls, they are design for maximum surface area.  Microbes tend to cling to the surfaces of the balls and break down some compounds like ammonia and nitrates.  Their is one gallon (they sell them by volume - don't ask) of balls in the tube.  4) Finally another layer of plastic window screen hold all the balls in place.  The filter itself is about 3 feet long, and is held to the drum by a PVC pipe holder.  

You can kinda see the green line (a garden hose - I wanted as few elbows as possible to try to reduce friction).  The garden hose is connected to the pump, a MAG Pump 1200.  The pump is rated at 1200 gallons per hour at zero head, and 400 gallons per hour at 14 foot of head, but it just doesn't look like 400 to me.  Hopefully I'm wrong!

As for the plastic lines running to and from the fridge.  During early July, 2002, Buffalo had what we would call a heat wave (low 90's).  Our house doesn't have central air, so the temperature in the tank skyrocketed.  The corals don't like, but will survive.  The fish on the other hand, well, let's just say I could have flushed some money down the toilet if I hadn't built the whole sump system. The water is run through the fridge from a small pump from within the sump, it doesn't keep the tank temperature down, but does help with the major temp swings.  I built the fridge lines so that their are no breaks in the line.  The pump runs the water through about 80' of tubing  (about 65' in the fridge) and then back using one piece of tubing.  The sump only currently holds 20 gallons, so between the extra water being in the basement (doesn't get much above 70 down there) and the fridge, the tank is OK.  I plan to up the sump capability to 40 gallons soon, so that should help even more.  I think a might be able to remove the fridge from the system with the reduced turnover rate in the sump (the water will spend more time in the basement and cool more).

If you have any questions give me a ring at pete@petejc.com.