Activated Carbon while cycling?

I wouldn't. It's not necessary. I'd save them for later when you need to take meds out of the tank.
Carbon is not really as necesary as the carbon-selling companies seem to think it is. : The only reason to use it is for removing meds like Gunnie said. It only works for a few days anyway.


If not using activated carbon, what is filtering the water other then the media sponge? (in the HOB case) The carbon also filters out odors and other fine particulates that the media cannot catch....or am I missing something here....? ???
Well right now there is the sponge and then this "biobag" which is supposedly a good place for bacteria growth. Other then that there is nothing right now. I do have activated carbon inserts and these inserts that are supposed to remove ammonia but I've been told to keep them out right now... while I'm cycling at least. Any agreements or other suggestions on what to do are always welcomed.


The biobag is usually filled with activated carbon. This is what you should change every 4-6 weeks. The media "sponge" is where the bacteria build up. This you should rinse in used tank water when doing your regular weekly water change ONLY when water has difficulty passing through it. Never rinse it in tap water, never wring it out dry. Just rinse and replace.

This is what I do and if I am doing something wrong, then someone please correct me.

There is not a need for carbon ever unless you are removing medication or if you have bad odors in your tank, but if you have that kind of odors there is more wrong than just what carbon can fix. Carbon only fixes odors for a day or so anyway.

There is also a chance of using too much carbon. There have been instances of fish becoming sick from carbon. I have been going through my books trying to find the article about it and cannot just yet, but anyway. you do not need it to cycle.

It won't KEEP your tank from cycling, it just isn't necessary.

If you start to get an unpleasant odor though you may want to use the carbon in the filter system for a coupla days or a week and then remove it.


Unless I am missing something, nearly every HOB filter has an activated charcoal (carbon) filter back that sits in the reservior. This actually filters the water of debris and odor....

Are you telling me that this is not necessary? Every fish tank I've ever owned has used some sort of fiber/carbon filter material.
Mechanical filtration--removes pieces of stuff--sponge/other media
Biological filtration--removes toxins--filter surfaces
Chemical filtration--removes odors and discolorations--carbon(charcoal)

Biological is necesary for the fish; mechanical just happens when water is sucked into filter; chemical in no way affects the fish, just some people like it. So carbon is not necesary...and actually it doesn't filter the water of debris, that's the job of the filter media.


So what you are telling me is that the biobag is useless, yet everything I've ever read and seen uses one where equipped.....?
The bio bag that Vin's talking about does mechanical, biological and chemical filtration, so no, it's definitely not useless.

mechanical because it filters large particles
chemical because it has activated carbon which does 'clean' the water
biological because beneficial bacteria can grow on the filter floss

In my opinion, using activated carbon can be beneficial if changed out on a regular basis and I think it does filter the water of dissolved organics. It's my understanding that if the activated carbon is not changed regularly then some of the dissolved organics that it absorbed can slowly get released back into the system.

I know many folks advise not using carbon and I don't use it on a regular basis in my freshwater tanks. However, I do use it sometimes in my saltwater tank to improve water conditions such as removing dissolved organics that don't get removed by the protein skimmer. This helps remove the slight yellowing of the water which allows better light penetration and a cleaner looking tank.

I think the problems arise when we forget to change the carbon. So if you do use it, be sure to replace at regular intervals. I don't think it will affect the cycle, whether you use it or not.


Thanks Mike. All I know is that every fish tank I and others have ever owned have used some type of floss/activated charcoal (carbon) filtration. The books and information I have read all recommend using some type of floss/carbon filtration in an HOB filter.......

I use the BioBags in my filter and change them every 4-6 weeks. My water is odorless, crystal clear and chemical free. So- unless I am doing harm, I plan to continue to use the BioBags.....So far, no one has told me that I am doing any harm.

And actually, I did a little more research....check out my post in the 'Filter Question' thread.......
Ohhh, I must not have read carefully enough, you were talking about a bio bag that provides mechanical, chemical, and biological filtration all at once. Of course that is good! Just a lot of people think the chemical part of it is relatively useless. But if it comes in the package of course there's nothing at all wrong with it.


Ohhh, I must not have read carefully enough, you were talking about a bio bag that provides mechanical, chemical, and biological filtration all at once.  Of course that is good!  Just a lot of people think the chemical part of it is relatively useless.  But if it comes in the package of course there's nothing at all wrong with it.

The AC in the bag is the same thing as the AC packet you put in to remove chemicals...........
What?? What I was saying is that there's no problem if the carbon comes incorporated in the media, just there's no point in buying it separately if it doesn't come with. Not sure if that's what you meant...


Nope. It's not what I meant. I just think we're confusing each other.....However, I'm not so sure I'm following your logic on the use of activated carbon....Either it's OK or not OK..... ???

You can buy your own filter bags and fill them with your own AC as well.....that's what I meant......
Top Bottom