Mrktplayer":2qzrb5zo said:
thanks, inexpensive too. What's the purpose of a filter sock? Reduce nitrate and/or eliminate detritus buildup in the sump?
Eh, depends on how it's utilized. Let me explain.
A poorly maintained mechanical filter will increase the amount of nitrates in your tank. You are essentially concentrating decomposing organic material in an area with high flow and oxygen (read--good bacterial breeding grounds) where it will decompose more rapidly than if it settled on the bottom of the tank. The end result of this decomposition is nitrate. Also, nitrate produced in a filter sock is (almost always) not near an anaerobic zone where it can quickly be reduced to nitrogen as is the case with live rock/deep sand beds/plenums/etc.
On the other hand...a well maintained filter sock can be very beneficial. If you are insane about your tank like I am and clean out your filter sock twice a day, you're removing particulates from your tank before they get a chance to decompose. Think of it like a protein skimmer in that you are removing (rather than trapping or converting within the tank) nutrients from the tank before they decompose. For this reason, I believe it is absolutely essential that if a filter sock is used it should be easy to access and easy to clean for frequent cleaning. Otherwise, out of sight, out of mind. It takes me about 3 seconds to remove my filter sock and 15 seconds to clean it off. In a perfect world I'd clean my filter sock every hour, but I've found I can do it every other day if I'm lazy without it affecting my nitrates too much.
Having said all that, a bit of nitrate is not all that bad for corals...
Atkinson, M. J., B. A. Carlson, and G. L. Crow. 1995. Coral growth in high-nutrient, low-pH seawater: A case study of corals cultured at the Waikiki Aquarium, Honolulu, Hawaii. Coral Reefs 14: 215-223.
http://www.springerlink.com/content/g2554037454q13wp/
They have other side benefits as well. An air water mixture passing through a fine filter sock will remove the microbubbles. They greatly reduce salt spray and noise where water enters your sump. When you turkey baste your rocks they're invaluable. They keep your water pretty crystal clear too.