Activated Carbon

[F15FreeEagle]

Do you use activated carbon? Why or why not?

[Diana]

I keep some on hand in case of emergency, or to remove medicines from the tank.
I have used it occasionally in that scenario.
I used to use it all the time. This was before I got into planted tanks.
Now my tanks are fully planted, and the more complex ecosystem usually does not generate the things that might need to be removed via AC.

[ScottFish]

Nope. Don't use it. My planted tanks, as Diana has just said, keep the tanks in great shape. Along with frequent WC and good water flow, I have not encountered any problems w/o AC.

[F15FreeEagle]

I do not use it either. As has been said, only to remove medications when that is necessary. I just bought a new canister filter, and I just that AC under the cabinet with the rest of it.

If you're doing water changes on anything resembling a regular basis, I do not feel that the stuff is of any benefit. I do use Seachem matrix though.

[PVT-Kanaka]

F15FreeEagle,

Nope. Gave up on it years ago. I just backflush all filter media. Saves money, and it has had no impact on fish longevity. Like Diana and you, it is ready to hand if required.

ERic

[F15FreeEagle]

Yep. After a lot of reading and conversations, I'm of the opinion that the stuff is mostly an unnecessary expense. Always good to have some on hand just in case you need to medicate the aquarium, but other than that...

[Hurriken]

If I could I'd like to rephrase the question. When would you use AC? (where, what, how)

[Diana]

Activated carbon has a great affinity for many things that could be toxic to the fish or other organisms (plants, microorganisms, other) in an aquarium. Many of these things are organic in the strict scientific sense (a molecule that contains carbon). The list includes pesticides, medicines, fragrances, dyes, and many other chemicals.
Most of these things do not get into or get created in a well run tank.
However, if something happens that these things show up, having AC on hand can save the tank. Obviously you need to be aware that the toxic chemical is showing up in time, before it affects the fish etc. Frequent water changes are good because they remove low levels of this sort of thing before you may even be aware that it is present. Water tests may show that something is not quite right, though the hobby level test kits will not show you what it actually is.

Many medicines are removed by activated carbon.
As part of the treatment schedule the medicine is added to the tank for a certain schedule, then removed. The best way to remove the medicine is with large water changes, then follow up with activated carbon to remove the remaining traces.

Chemicals that cause odors are removed by activated carbon. I happen to like that slightly earthy-alive sort of smell, and in a well run tank this is so faint that I have to have my face really close to the tank to smell it at all. However, sometimes it does get a bit stronger, and running AC in the filter can remove it.

Chemicals in the house can be bad for aquarium life. Perfumes, air fresheners and many other things should not be allowed to enter the aquarium system. If you regularly use these things in the same room with an aquarium you might want to run AC most of the time in the aquarium filter.

A tank with some equipment failure that reduces the water circulation can allow low oxygen areas to develop, and this can create unpleasant odors. Obviously monitoring and maintaining the equipment is the best prevention, and promptly fixing problems is important. Then a big water change, followed by adding AC to the filter can remove the bad smelling chemicals from the tank.

So:
No matter what the reason, the basic way to use AC for emergency chemical removal begins with a big water change. This removes the greatest quantity of whatever I want to remove. Could be 2 x 50% back to back water changes(result is a 75% water change). Then add AC to the filter. I might add some for about 24 hours, remove that then add some more. Reasoning: the chemical I am removing starts to build up in the AC pretty fast when there is a lot of whatever it is in the tank. Plus, other things can get removed by the activated carbon. The AC gets full. So remove that first dose of AC and add a second. That second dose will be pretty good at removing the significantly smaller amount that is left after the first dose is full.

Activated carbon does have some limitations.
It is not so great at removing inorganic molecules such as minerals or water hardness molecules.
It requires a certain flow rate.
It does not remove debris particles from the water. In fact, the presence of such particles in the water can clog the AC before it accomplishes the goal of removing whatever it is you are using it for. It does not take a large amount of particles to clog the AC.

Best way to help AC do its job is to clean all the filter media and stack it in a way that will remove the coarse and fine debris with sponges and floss before the water passes through the AC. In other words, set up the filter so the mechanical filtration is done before the water reaches the AC. If debris is clogging the AC, but you think the AC can still be used for removing chemicals, then rinse the AC (and the other filter material) and set it up again.

Unfortunately, about the only tests there are to tell if AC is still working or is full are not very good.
One test is to smell the aquarium. Our noses are not very good, though. If we can smell something at all it is probably already at too-high a level in the tank.
Another test is to monitor the fish, plants and other macro-life in the tank. Unfortunately, by the time these are reacting to whatever it is, it may already be too late.
Hobby level test kits do not test for most of the things AC removes from the tank. Testing on a regular schedule may show you that something is changing that probably needs attention. (Hey! The TDS is higher than it was last week... What is going on?)

[Diana]

https://www.thoughtco.com/how-does-acti ... ork-604294

Here is a pretty good, short article about AC.