Mechanical and Biologic Filter

[denierlexiese]

My saltwater fish book suggests setting up an undergravel filter for a beginning salt water noob. My new DAS tank comes with a built in filter, and I also thought with salt water tanks, just having enough live rock was a filter enough? Should I be using an undergravel filter? If I just use live rock, how many lbs do I need for a 55 gallon?

Thank you.

[Typical Tony]

http://www.dfwfishbox.com/forums/production/showthread.php?t=18082

Second, Lbs of Live Rock per Gallon. Often we are told that it is necessary to keep at least 1 to 2 lbs of live rock per gallon of aquarium capacity in order to establish a working filter for our reefs. This is completely misleading. The ability of live rock to act as a natural filter, and the primary filter that will keep your reef's water clean, is dependent on the surface area of the rock itself, which is also related to how porous it is. Lets say you purchase 40 lbs of limestone or other dense "base rock" to fill your 40 gallon aquarium thinking you are fulfilling the 1 lbs per gallon rule. This rock can be encrusted in coraline algae and be well-aged but it is not providing you with the same filtering ability as say 10 or even 5 lbs of Fiji or Tonga rock. In the latter case your actually providing a much better filter for your system by purchasing less because it has much more surface area for denitrifying bacteria to inhabit and is also full of other creatures that will help you maintain a biological diverse and clean ecosystem.

http://www.melevsreef.com/tanks.html