High density, usually pink or blue, but not the white.

Ya High Density Styrofoam

http://i675.photobucket.com/albums/v...2/DSCN1972.jpg

The photo is a little old, the refugium now has a big ball of cheato in it and there's a silicone pad under the pump, but you get the idea. The drain is split so that some of the flow goes to the skimmer compartment and some goes to the refugium (on the far right). The drain flow is controled by a ball valve on the skimmer side. The more closed it is, the more flow is directed to the refugium. I shoot for 75% to the skimmer, 25% to the refugium. The blue bin on the right is a recycle bin that I'm using for an auto topoff reservoir, the duct tape and acrylic lid is to reduce evaporation from the reservoir. My ATO rig consists of a double float switch and solonoid setup which controls a Maxijet 400 powerhead in the bottom of the reservoir that send fresh water to the center compartment of the sump through vinyl tubing. The float setup can be obtained from a non-sponsor website, PM me if you want. There's also a TLF reactor running phosban, carbon in a media bag, as well as essential tank maintenance equipment (turkey baster, feeding tongs, mag float, towel, net, etc.).

Edit: Wow, must have just cleaned the skimmer before taking the pic, I can't remember the last time the cup was so clear!

Well here's mine:

Attachment 5546

Not much of a pic, but basically a marineland sump with a biowheel, skimmer, and 2 heaters.

90g Zeovit sump.
 

Okay I will play. Here are some pic's of my 90g Zeovit sump. Nothing special, just 45"x15 1/2"x16" sump I custom built, 4000 quite one pump, ASM G2 skimmer, Vertex 3L Zeovit reactor, 300w Aqua clear heater and Tex t5 4x24w.

http://i884.photobucket.com/albums/a...k/IMG_2151.jpg

http://i884.photobucket.com/albums/a...k/IMG_2152.jpg

:biggrin:

Here is what is directly under my tank:

Here is the closed loop.
http://i600.photobucket.com/albums/t...g?t=1263708097

This is directly under my tank in the basement (my tank is on the main floor). Top tank is water change tank - it's part of the system (75 gallon). The middle tank is frag/grow out tank (40 gal). Bottom is 100gallon sump.
http://i600.photobucket.com/albums/t...g?t=1263708175

http://i600.photobucket.com/albums/t...g?t=1263708267

It's all a matter of how much time you have :)