Activated Carbon: How Long Will it Really Last?

Activated carbon is one of the most popular filtration media for home aquariums. But they only last for as long as the carbon is still able to absorb impurities. One it loses its charge, you’ll need to replace it.

So, How long does activated carbon last in aquarium filters? You should change your activated carbon every 2 to 4 weeks. If the water is very dirty though, you may have to change it every week instead.

With new filtration methods becoming available, some people wonder whether activated carbon is still needed.

If you’re not sure whether you should add it to your aquarium’s filter, you’ve come to the right place. We’ll answer this and many other questions for you.

What is Activated Carbon?

Activated carbon is bituminous charcoal, lignite, or wood that has been treated at very high temperatures to “charge” it. This creates lots of tiny pores to increase the surface area.

Because of this, the activated carbon is able to act like a sponge. Bad odors and trace elements are easily absorbed for as long as the carbon holds its charge.

You should be aware that there are different types of activated carbon that are made using different methods. For aquariums, you need one that is made from bituminous charcoal and comes in granular form. This type is called a granular activated charcoal, or GAC for short.

What Does Activated Carbon Do?

Your aquarium water contains lots of dissolved contaminants that need to be removed. These can include tannins (which change the water’s color), phenols (which cause odors), chloramines, and chlorine. Activated carbon is able to absorb these elements, leaving your aquarium clean.

But you should also know that there are some things activated carbon cannot absorb. You can’t use it for toxin removal, for example, because it cannot absorb nitrate, nitrite, or ammonia.

Activated carbon also cannot absorb heavy metals like iron. If your water has any heavy metals, you should use a water treatment product first.

Sometimes you’ll need to treat sick fish with medication. Activated carbon will absorb most medications, so you should take it out before you start treatment. Once your fish are healthy again, you can safely put the carbon back into your aquarium filter.

How Long Does Activated Carbon Last?

Some people think that activated carbon will last for months at a time. Others think it only lasts a few days.

The truth is, how long your activated carbon lasts depends on a lot of different things.

Different brands use different temperatures to charge the carbon, which can make it last longer or shorter than other brands. Usually, it will last between 2 to 4 weeks.

The dirtier your aquarium water, the shorter your activated carbon will last. This can also happen when you have corals or microalgae in your aquarium, because they constantly release biochemicals into the water. Activated carbon will help you get rid of those biochemicals by absorbing them.

Even though activated carbon is one of the most absorbent filter media, the more it absorbs the quicker those tiny pores get blocked. Eventually, so many of the pores are clogged that it cannot absorb anything anymore.

When this happens, your activated carbon loses its charge.

You should change your activated carbon every 2 to 4 weeks, depending on the bio load in your aquarium. If you have a turtle, for example, you’ll need to change it once a week instead.

How to Change Your Activated Carbon

Your activated carbon needs to be placed into a mesh filter bag to be used. You should put half a cup of carbon into the bag for every ten gallons of water in your aquarium.

Sometimes you’ll find it has some carbon dust when you take it out of its container. Just to be safe, before putting the activated carbon into your aquarium, you should run it under some running water from a tap.

Next, you should remove the old carbon from your filter system so you can put the new bag in. Your filter should have 3 kinds of media: mechanical, biological, and chemical.

The mechanical media will help make sure that your activated carbon doesn’t have to absorb too much debris too quickly. And the biofilter will absorb some of the organic compounds that can clog your activated carbon media.

That’s why you should place your activated carbon (the chemical media) after these 2. Keep your water flow direction in mind: the activated carbon should be the last media the water flows through. Otherwise, it will lose its charge very quickly.