I found this fascinating (GAC Usage)


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I don't have a reactor; will not have one with my current setup. I use carbon, in various forms, in "passive" mode; in a sock draped over the overflow in my 'fuge.
I've been researching the best way to use GAC effectively in my setup and ran across this:
As I mentioned in Part One, the typical power filter for carbon use moves water past the carbon at a much faster rate than research recommends. A popular canister filter for carbon use has a flow rate of 250 gallons per hour. Evidence suggests that adsorption rates decline when water moves past the carbon faster than 65 milliliters per minute, roughly one gallon per hour. Spotte recommends that no more than one tank volume be circulated through the carbon per day. Using Thiel’s 12-hour guideline combined with Spotte’s one tank volume suggestion, translates into a flow rate of about 4 gallons per hour for a 50-gallon tank. Clearly, using a power filter for carbon is not the best approach.


Granular activated carbon is a valuable tool for the reef hobbyist. It can play a significant role in maintaining a healthy tank. The hobby’s traditional approach to the use of carbon, however, has been misguided. Optimum use of carbon requires only periodic use. Slow circulation of water through small amounts of carbon will remove significant amounts of color. Passive use of carbon, as well as circulation through high-volume power filters should be avoided.
The above from:
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What are your opinions?