How Often to Change Carbon Filter in Fish Tank?

Do you have a fish tank with a carbon filter? If so, you might be wondering how often you should change the carbon filter in your tank. We will get into that question, of course, but first, let’s discuss what carbon in your tank actually is.

Understanding AC, or Activated Carbon

Using activated carbon, known as AC, or even activated charcoal, is an extremely popular method to keep home aquariums clean and healthy.

The activated carbon is placed in your filter, and as water moved through, the carbon cleans it.

However, the carbon, or charcoal, doesn’t last forever. Once it is done absorbing the impurities in your tank, it simply stops working.

Ideally, you should be changing your activated carbon every two to four weeks, but if you notice that your water is getting dirty before that, you might want to start changing it weekly, instead.

What is AC, or Activated Carbon?

Activated carbon can be made of a number of materials, like wood, or materials that have been turned into charcoal.

When treated at extremely high temperatures, the carbon is considered to be “charged.” If you look at the surface, you will see teeny holes, or pores, in the carbon.

This allows the carbon to act just like a sponge would. In other words, it absorbs elements and odors from the tank as long as the carbon is “charged.”

There are a number of different types of activated charcoal on the market, but only one type is appropriate to use in an aquarium. It’s called bituminous charcoal.

This carbon is available in a granule form, and it might also be called GAC, or granule activated charcoal.

Is Activated Carbon Necessary in an Aquarium Filter?

First, you might be wondering if activated carbon is even necessary in your tank. To let you know why you should have AC in the filter, we are going to tell you what it does.

If you ever have looked at the water in the aquarium, you might notice that there are small particles floating around. But, you can’t see everything in the water.

Some of the things you can’t see include phenols, which cause odor from your tank, and tannins, which can change the color of the water. There are also elements like chlorine and chloromines in the water.

However, you have to be aware that there are some things in the water that are not absorbed by activated charcoal. For example, it doesn’t remove any toxins like nitrate, nitrite, or ammonia.

Additionally, activated charcoal doesn’t absorb iron or other heavy metals. If you have these in your water, you need to treat the water chemically.

Another thing that activated charcoal will absorb is medication. However, you want to keep your medication in the tank if the fish need it.

So, if you are treating an ill fish, you should remove the carbon from the filter.

How Long Does Activated Carbon Last?

Some people falsely believe that they can keep activated charcoal in the filter for months. This just isn’t the case.

The truth is, depending on the type of tank you have, and the environment, this could determine how long the activated carbon lasts.

There is also the fact that different brands of activated carbon lasts longer than others. Some might last only two weeks; other brands might last three or four weeks.

You also have to consider how dirty your tank is. In a tank that gets dirty pretty quickly, you might only want to keep your activated carbon in for one to two weeks before changing it out.

If you have corals that release biochemicals into the water, you might also have to change the AC more often.

Also, if you have animals like snails in your tank, they might help to keep your water clean; if you have turtles, it’s very likely that your tank will get dirty, faster.

Though activated carbon is really great at filtering the water, once the small pores are full of contaminants, it stops being effective.

Changing Your Activated Carbon

Finally, let’s talk about how to change your activated carbon.

In order to be used correctly, it is placed in a mesh bag. A good rule of thumb is to put a half cup of activated carbon in the bag for every 10 gallons of water is in your tank.

It’s best to run the filter bag under water to remove any dust, and then set it aside.

Next, take out the old activated carbon and filter back from the filter system and discard it. That leaves space for the new filter bag to be inserted into the filter.

Once it’s in place, make sure the filter is working correctly, and then breathe a sigh of relief! You have made your fish tank a nice, clean home for your aquatic creatures.