very hard question to answer briefly..I think.
the term refugium simply means...a seperated area that provides safty/shelter to something.
initially, I believe a refugium was meant to house things like fish that were getting beat up by others...or a hitchhiker that you were nervous might be a reef killing monster.
But since then...the term has kind of taken on a new meaning. While it can still be used to mean everything above...it seems more commonly used in reference to an area that houses macro algae and is usually on an opposite photo-cycle than the display tank.
Now...it seems, the main point of refugiums seems to be any combination of the following:
- Stabalize pH. Normally the tank's pH will rise during the day while the lights are on...then drop over the evening. With a refugium on an opposite photo-cycle...the pH tends to stabalize.
- Nutrient export. When algae grows...it binds up nutrients in it's "body". So you can promote algae growth in the refugium as opposed to the display...and because you would trim it frequently, you'd be using the trimmed algae as a means to get the bad nutrients out of your tank.
- Pod production. Lots of people use refugiums to give the 'pods a safe place to breed and live. The pods thrive in the refugium...and frequently get sucked into the tank..where pod loving critters promptly gobble them up. Great for tanks with Mandarins and the like. The tank itself can't provide enough area for enough pods to populate to keep a pod-gobbler like the mandarin fish full.
hope that helped a bit. If not, and I was just babbling (which I tend to do), please come back with more questions!!!
