How often should you change carbon

[Jon]

I am running a cup of carbon in my filter sock for my 58 gallon tank. How often should I switch out the carbon and replace it with fresh carbon?
Jon

 

[mnat]

From what I have read monthly seem to be the overall concensus under normal circumstances. I change it out monthly as well. I am sure others have differenet schedules, but whatever works best for you is the answer.

 

[pgordemer]

Carbons differ highly in quality and ability to absorb. Though many will disagree on how long a certain brand of carbon will last, all will agree it depends on bio load. Carbon absorbtion drops off quickly in the beginning, then levels out before it stops absorbing.

2 weeks - up to a month is what is said, with 2 weeks being the most common.

My logic is to use higher quality/cost carbon in smaller amounts changed more often. I use 1/2 cup of Rox .08 changed every 2 weeks.

 

[Boomer]

GAC can go a month in most systems and should be removed and washed well 1 / wk and replaced 1/ m. If one is using a reactor then 1/m without cleaning, as reactors are mostly self-cleaning. As has been point out all GAC is not the same nor is the bioload. Furthermost, flow rates may differ form on individual to another and then there is what is it adsorbing. So, there is no set mark one can really go by. Based on lab tests done by Dr. Ken Feldman, from PSU, for most GAC 1/2 cup 50 net gals with ROX 1/3 cup / 50 gal. Some may need more and some may need less. One can also run some simple Methylene Blue test on there used GAC to see if it is still effective. I have a guy who volunteered to do this, after reading some old RC Chem posts of mine and who will try to collect some data points and put it up for an article but I have not heard back from him yet or if he even started it yet. This was early this last spring. MB is a low molecular weight, organic-inorganic dye, often used to treat fish eggs from fungal infections, to reduce Nitrite toxicity in FW fish and as an O2 carrier. Many GAC actually have a MB number, which give an indication of a GAC to remove med sized molecules. The test is rather simple, a drop or two of MB in a 5 gal bucket, with the so called spent GAC, where it is set up so water flow through the GAC and then take note of long it takes for the water to go clear vs the same GAC amount that is virgin. In short, what one does with GAC, in regards to type, how much and when to replace it is a choice that works best for you. One also needs to be careful if running SPS tanks, for example, where you are running some **** e-bay GAC @ 1/2 cup /50 gal and then jump to ROX. This can crash the nutrient load to quickly and cause serious issues with corals if done to quickly. ROX adsorbs almost 1.5 - 1.75 times more than other GAC in this hobby.