To use or not use activated carbon?

[fishtk75]

I read many theads here about activated carbon.
Some say to use it 24/7 some say never use it only when using it to get meds out because of PO4 using it 24/7.
I been using activated carbon for years has some way of looking at activated carbon changed of using it?
I like to know if there is news of this.

[HighlandReefer]

DOC (dissolved organic carbon) in the reef tank still remains a mystery for the most part. GAC will remove some kinds of DOC and perhaps not others. Water changes remove everything that is in the removed water, but are they enough to maintain the recommended levels of DOC in the reef tank to keep the occupants happy? JC Delbeek has stated that perhaps the nitrate level found in a reef tank can be used as a rough gage to determine DOC in a reef tank. #1

#1: Marine Aquarium Chemical Filtration JC Delbeek
http://74.125.155.132/scholar?q=cache:DPCe-5kvZbUJ:scholar.google.com/+activated+carbon+in+a+reef+tank&hl=en&as_sdt=0,9

The main problem is we as hobbyists do not have the capability to measure the amount of DOC in a reef tank much less its components. So it is impossible for one to say whether running GAC in your tank vs another hobbyist's tank is appropriate. High levels of DOC lead to tissue necrosis in coral. Low levels prevent the coral from growing properly.

Certainly a lot of the DOC in a reef tank is acted on by bacterial, algae & other microbes found in a reef tank and many of these microbes can be skimmed out which will reduce the total DOC, but is this alone adequate?

Many heavy metals are added in quite large amounts in a reef tank & GAC will help remove them, but the question remains does skimming remove enough of these heavy metals by removing the bacteria, algae....etc. We can't measure heavy metal levels as hobbyists. Heavy metals at high levels cause tissue necrosis in coral. The little research we have available regarding skimmers indicates that the amount of heavy metals removed by skimming is not large, which would imply running GAC for this purpose may be one of its greatest benefits.

The only way a hobbyist can determine how much GAC needs to be used to remove DOC is to watch their organisms for negative signs, unless they have the bucks for expensive testing procedures. This will depend on the type and amount of fish present, the amount you feed, perhaps the type of micro-organisms *& coral present in your system, and many other factors. Perhaps tank water coloration can be used to some extent as a rough gage. With the complication of high heavy metal levels causing coral tissue necrosis and too much DOC causing coral tissue necrosis & the toxic forms of DOC produced by bacteria, coral....etc, causing coral tissue necrosis, it may be easier to run GAC and supplement dissolved organics through feeding if signs of poor coral growth appear. ;)

The bottom line is that there is a lot of guess work regarding running a healthy reef tank and when things go wrong, it can be difficult to discern. :)

[HighlandReefer]

A few articles that may be of interest in respect to running GAC:

Reef Aquaria with Low Soluble Metals
http://www.reefkeeping.com/issues/2003-04/rhf/feature/index.php

What is Skimming?
http://reefkeeping.com/issues/2006-08/rhf/index.php

Organic Compounds in the Reef Aquarium
http://reefkeeping.com/issues/2004-10/rhf/index.htm

TOXICITY OF TRACE ELEMENTS: TRUTH OR MYTH?
http://www.advancedaquarist.com/issues/may2003/feature.htm

[Randy Holmes-Farley]

I run GAC 24/7.

There are some potential reasons to not use it, but I think its clear benefits ( :D) outweigh any hypothesized (but not demonstrated, IMO) detriments.

because of PO4 using it 24/7.

I do not think release of phosphate is any substantial concern when using a good quality aquarium GAC in any manner, whether it is intermittent or 24/7.

[tmz]

I also run granulated activated carbon 24/7 and have for years . I run purigen too.

[HighlandReefer]

"I been using activated carbon for years has some way of looking at activated carbon changed of using it?"

Carbon dosing may be the latest development which can change how we decide to use GAC. ;)

Carbon dosing can greatly increase the number of bacteria in a reef tank. GAC is a great medium for bacteria to attach and develop on. Once bacteria films develop on GAC, they can quickly clog the very small spaces used to collect and attach DOC on. As the bacteria grow in numbers they spread and occupy the spaces between GAC granules which prevents water from circulating through a reactor or filter bag.

How long is the GAC effective while carbon dosing. Perhaps the period of time that GAC is useful is greatly reduced by 1/2 or even 2/3 the amount of time?

Are the bacteria that develop on GAC while carbon dosing more effective than GAC at removing DOM and heavy metals? If so, it may be better to use a very large GAC reactor and simply rinse bacteria from the reactor when it clogs (In this case, perhaps using the cheapest GAC will work as well as the expensive types). If the GAC is more effective, it may be better to replace GAC more often when carbon dosing.

IME, GAC clogs completely while carbon dosing in 1 month at the most and when I increased vinegar doses, it took as little as 2 weeks to clog the GAC reactor. When I was not dosing vinegar the GAC could last 2 months without clogging. :)

[HighlandReefer]

It is my understanding that you can't regenerate GAC using hydroxide for the purpose of re-using GAC without the effect of bacterial growth.

How effective would using hydroxide be for breaking down & removing DOM and bacteria (plus the secretions produced by bacteria) collected on GAC for re-using it in a bio-reactor only? Hopefully using hydroxide on GAC would extend the period of time it would take to clog a bio-reactor. Of course this is assuming that using a bio-reactor full of GAC along with carbon dosing would be more effective than GAC alone without bacterial activity (carbon dosing). ;)

[elijaher]

Maybe that why reefer use GAC/GFO at the same time.

[fishtk75]

Thank you all for your reply. It helps me that I was ok. I will keep 24/7 GAC and GFO. I seen a change if I do not use it in the water that its clearer.