GAC
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TheEngineer
Formerly icecool2
You're gonna get a lot of opinions on this 
People who run it seem to run it 100% of the time. There are people who run it passively in a bag and those that run it in a reactor.
The downside is that they start to release stuff back into the water column, supposedly, once the GAC is exhausted. There's not a clear way to test when that's happened.
People who run it seem to run it 100% of the time. There are people who run it passively in a bag and those that run it in a reactor.
The downside is that they start to release stuff back into the water column, supposedly, once the GAC is exhausted. There's not a clear way to test when that's happened.
Servillius
Active Member
My guess is this thread will get entertaining.
Granular activated carbon is used in a range of industries including water purification. It is used because many organic molecules will adsorb on its surface. Generally speaking this means more complex organic molecules, carbon will not bind nitrate, phosphate, etc. in notable quantities. The types of molecules were talking about here correspond very loosely to color giving molecules. Tannins, natural organics, etc.
By removing these, carbon not only clarified your water, but removes potential toxins. Lots of natural toxins fall into this category.
It is clear if you run carbon too aggressively you can have a negative impact on a tank, but generally speaking, if you follow the instructions, that’s hard to do. My guess is many more tanks bite it from “unknown causes” while not using carbon than from carbon use. I tend to go with the Korallen Zucht recommendation which is to use high quality carbon in a bag and give it a good shake every few days then replace it every 30 days.
Granular activated carbon is used in a range of industries including water purification. It is used because many organic molecules will adsorb on its surface. Generally speaking this means more complex organic molecules, carbon will not bind nitrate, phosphate, etc. in notable quantities. The types of molecules were talking about here correspond very loosely to color giving molecules. Tannins, natural organics, etc.
By removing these, carbon not only clarified your water, but removes potential toxins. Lots of natural toxins fall into this category.
It is clear if you run carbon too aggressively you can have a negative impact on a tank, but generally speaking, if you follow the instructions, that’s hard to do. My guess is many more tanks bite it from “unknown causes” while not using carbon than from carbon use. I tend to go with the Korallen Zucht recommendation which is to use high quality carbon in a bag and give it a good shake every few days then replace it every 30 days.
Flippers4pups
Fins up since 1993
As others have stated, there's a great deal of debate on it's use. One that comes to mind is HLLE:
https://www.advancedaquarist.com/blog/activated-carbon-affirmed-as-causative-agent-for-hlle-disease
BRS has some good videos on GAC, here's one of many:
Greybeard
2500 Club Member
As with most of us, all I can do is share my personal experience... take it as you will.
I have a dual BRS reactor. Normally, it's off. Empty. I do water changes regularly, yellow water isn't usually a problem for me. IF I note that my corals don't look so good, polyp extension poor, etc. I might run a cup of GAC for a few days, see if it helps. IF I _KNOW_ that I've dumped something in the tank, let something rust, or had some other form of contamination, I might run a cup of GAC for a few days. IF I note that one of my corals has died, a bunch of macro algae has rotted away, that kind of thing... I might run a cup of GAC for a while.
Otherwise, no, I don't run it all the time. Pointless, at best, and possibly even harmful.
The only people I know that run GAC all the time don't do water changes, and they either run it passively, in a bag, or in an undersized, slow flow reactor.
It's a tool. A good one... for removing unknown contaminates. That, along with a polyfilter, are about the best tool you can have in the box, for those occasions when something isn't right, but you can't pin down a cause. Water changes, the 'other' tool for this kind of thing, are equally important. The two, combined, can really help, when something is contaminating your aquarium.
The trend these days is towards KNOWING what goes in your tank. ICP testing, more and more accurate test kits, meters, probes, monitors... Unfortunately, sometimes something that you don't really know, and can't test for, gets in there. Airborne contaminates, dying critters, contaminated hands, accidentally dropped 'stuff'... it happens. GAC is good for that. It'll help pull lots of different 'stuff' from the water column. IMHO, that includes a good number of things that we WANT in the water.
I put GAC and GFO in the same category, excepting that GFO is _specific_, and GAC is general. Don't be afraid to use it, if you need it... but a properly set up, well maintained, happy aquarium should not need it.
I have a dual BRS reactor. Normally, it's off. Empty. I do water changes regularly, yellow water isn't usually a problem for me. IF I note that my corals don't look so good, polyp extension poor, etc. I might run a cup of GAC for a few days, see if it helps. IF I _KNOW_ that I've dumped something in the tank, let something rust, or had some other form of contamination, I might run a cup of GAC for a few days. IF I note that one of my corals has died, a bunch of macro algae has rotted away, that kind of thing... I might run a cup of GAC for a while.
Otherwise, no, I don't run it all the time. Pointless, at best, and possibly even harmful.
The only people I know that run GAC all the time don't do water changes, and they either run it passively, in a bag, or in an undersized, slow flow reactor.
It's a tool. A good one... for removing unknown contaminates. That, along with a polyfilter, are about the best tool you can have in the box, for those occasions when something isn't right, but you can't pin down a cause. Water changes, the 'other' tool for this kind of thing, are equally important. The two, combined, can really help, when something is contaminating your aquarium.
The trend these days is towards KNOWING what goes in your tank. ICP testing, more and more accurate test kits, meters, probes, monitors... Unfortunately, sometimes something that you don't really know, and can't test for, gets in there. Airborne contaminates, dying critters, contaminated hands, accidentally dropped 'stuff'... it happens. GAC is good for that. It'll help pull lots of different 'stuff' from the water column. IMHO, that includes a good number of things that we WANT in the water.
I put GAC and GFO in the same category, excepting that GFO is _specific_, and GAC is general. Don't be afraid to use it, if you need it... but a properly set up, well maintained, happy aquarium should not need it.
Flippers4pups
Fins up since 1993
Well said.
