chrisjet;49163 wrote: I have a 90g with 20g sump and fuge. I want to run carbon but am unsure about how much to use. As for right now I have about 1 full cup's worth in a piece of panty hose that is sitting in the sump. I am not sure if I am using the correct amount. Also I have heard to change out the carbon every 3 months. Please tell me how you feel about running carbon and how much i should use etc.
Thanks,
Chris
There's a lot of conflicting information out there on granulated activated carbon (GAC). One thing that a lot of people do agree on though is amount to use, which is generally accepted as 1 tbs per gallon. Keep in mind that not all GAC are created equal, since there are many variables in the manufacturing process including original source, method of activation, and acid washing. Generally speaking, granular bitumous that is steam activated and acid washed is the best. Why do we care to use better GAC? All GAC adds phosphates, some silicates, and some sulfar to your system. The better stuff adds less of the bad stuff. Its a lil crazy that we use GAC since we really don't want to be adding those compounds to our system! Clearly its because the benefits in using it outweigh those negatives.
There are different methods for running GAC, some of which are more effective than others. Obviously, actively running it in a reactor or through a canister filter will be more effective than running it passively in a bag as you do. However, I run my GAC in a bag as well and although its not as efficient, it still gets the job done albeit at a slower rate. The slower rate also means that it won't become saturated as quickly, which for me is just fine.
So that leads us to the final question of how long to leave it in there. There is evidence that GACs will leech some of their absorbed compounds back into the water over time. Some other people claim any leeching is minimal. I dunno what the answer is, so I'm more conservative and replace mine as soon as its no longer effective. How long is it effective? This will vary depending on your bioload and many other factors, including whether you run it actively or passively. Fortunately, you can test this yourself with some methyl blue. If it absorbs the MB then its still effective
. When I tested this it seemed to be very effective up to 4 days. It was still effective after 1 week, but after 3 weeks the GAC only slightly made a difference. As such, I've been changing my GAC out every 3 weeks. Keep in mind that I run my GAC passively, and of course its effectiveness varies from tank to tank, as each tank is more of a sesspool than others.
As for using GAC as a biological filter, there are many more effective ways of biological filtration out there that don't have any potential negatives that piles of saturated GAC might have. I am a firm believer though that you can increase your biological filtration such that your nitrates are never an issue. That however is a whole nother topic of contention
.
G'luck.
