Is activated carbon bad for planted tanks?

Author: Dr. Brandt O'Conner  |  Last update: Tuesday, February 17, 2026

The (permanent) use of activated carbon as a filter mediumin a planted aquarium, which is fed with liquid fertilizers according to the plants' needs, doesn't make much sense. Although the activated carbon ensures clear water, it unfortunately also binds metals that are important nutrients for the plants.

Is activated carbon bad for planted aquariums?

Overall, using activated carbon in your aquarium filter is a good thing, but not a must. If you test your water regularly, do partial water changes and treat new tap water (regular tank maintenance)- in most cases there is no need to use activated carbon.

Does activated carbon affect plant growth?

Adding activated carbon (AC) to the soil affects plant growth and may reduce certain soil microbes and bind allelochemicals. In the laboratory, activated carbon (AC) reduces these advantages exhibited by non-native plants by binding to organic compounds.

What is the main disadvantage of activated carbon?

Disadvantages of Activated Carbon Filtration

Short lifespan: An activated carbon filter has a maximum filter capacity (the maximum amount of contaminants that can be trapped in the media until the media is eventually fully clogged).

Can I use aquarium activated charcoal for plants?

No, the activated carbon in ``used water filters'' cannot be used for garden soil because it is harmful. The activated carbon in these filters contains chemicals that can be released into the soil and contaminate it. These chemicals can potentially harm plants and animals that come into contact with them.

5 Things You Need to Know About Using Carbon In Your Fish Tank

Can you use activated carbon in terrariums?

Steps To A Tropical Plant Terrarium

Add activated charcoal on top of the rocks. Beware, this is a very messy product so you may opt to wear gloves and go gently as the charcoal will release a black dust. The charcoal helps absorb any sitting water and prevents odors and bacteria build-up.

Does carbon remove plant fertilizer?

Activated carbon is used to absorb odor and tannins and adsorb larger molecules well - these usually mean organic compounds with large molecular chains (such as medicine). It does not remove most fertilizers in a planted tank, contrary to popular belief as the molecules are too small to be captured.

Why is activated carbon bad?

Activated charcoal is likely safe for most people if you only use it for a short time. There are some possible side effects, like constipation. In rare cases, it can cause blockages and dehydration. It also can stop your body from absorbing some drugs.

What are the hazards of activated carbon?

Contact with strong oxidizers such as ozone or liquid oxygen may cause rapid combustion. Explosion: Fine dust dispersed in air in sufficient concentrations, and in the presence of an ignition source is a potential dust explosion hazard.

What are the negatives of activated charcoal?

Activated charcoal is safe for most adults when used short-term. Side effects of activated charcoal include constipation and black stools. More serious, but rare, side effects are a slowing or blockage of the intestinal tract, regurgitation into the lungs, and dehydration.

Can I put activated carbon directly in an aquarium?

It is recommended by aquarium experts that aquarium activated carbon be used in the last stage of filtration. At this stage the water usually arrives without particles that affect the adsorption capacity of the aquarium activated carbon.

Which plants like charcoal?

Succulents. Charcoal mixes are ideal for creating succulent potting mixes because they keep the soil from getting soggy.

Will activated carbon help with algae?

Activated carbon helps by removing these elements, making it tougher for algae to take over. Activated carbon is a cost-effective way to enhance water quality, so you can enjoy a healthier aquarium without breaking the bank. It's a small investment with big rewards!

Does activated carbon hurt fish?

Does activated carbon hurt fish? If you use activated carbon not correctly, you can expect some irreversible changes. Some cases have been reported that powdered activated carbon can get trapped in the fish's gills.

Can too much CO2 hurt aquarium plants?

High levels of CO2 also affect aquarium plants. While aquatic plants use CO2 for photosynthesis, excessive amounts can lead to nutrient imbalances. The signs of too much CO2 in plants include discoloration, weak stems, and slow growth, depending on the plant species.

Does activated carbon remove ammonia?

Impregnated activated carbons are more effective at removing ammonia (NH₃) than standard activated carbons, as the high kinetic energy of the ammonia molecules means there is a lack of attraction to adsorption sites.

What are the disadvantages of activated carbon filter?

Activated Carbon (AC) filtration, as with any water treatment method, is not capable of removing every possible type of contaminant. For example, sodium, microbes, fluoride, and nitrates cannot be removed with AC filtration. Water softening also cannot be achieved with AC filters.

Is activated carbon safe for the environment?

One advantage of activated carbon is that it can adsorb a wide range of different toxins and pollutants. Naturally, these are all incredibly important processes that both prevent and mitigate environmental damage and toxicity.

How many times can you use activated carbon?

Good News! You can re-use your carbon 4-5 times if you follow these cleaning steps… Gather your materials: You will need your activated carbon, a large container, a strainer, a stirring spoon, and water.

Does activated carbon hurt plants?

Researchers find that activated carbon added to the soil can change the way plants and soil organisms communicate with each other. Changing this communication can improve native plant growth.

Will activated carbon lower nitrates in an aquarium?

Carbon does not remove ammonia, nitrite or nitrate from water. It also does not have an effect on water hardness or alkalinity. Some carbons will leach phosphate into the aquarium water.

What is the difference between carbon and Purigen?

Purigen is for removing only nitrogenous waste, changed after it becomes brown. While activated carbon, changed bi-weekly, absorbs almost anything. All 3 stages of filtrations are recommended.

Can I put activated carbon directly in an aquarium without?

Activated carbon will lose its effectiveness rather quickly if exposed to lots of debris from the aquarium. Therefore, carbon should be placed after the mechanical filtration media in the filter.

Does a heavily planted tank need a filter?

A significant increase in this surface through the use of high-performance filter media is actually rather counterproductive in a heavily planted aquarium, since important nutrients like nitrogen compounds are broken down by bacteria, instead of keeping them available as food for the aquatic plants.

Is Purigen safe for planted tanks?

The filter medium Purigen by Seachem is an absolutely unique product, and every aquarium keeper should use it! It doesn't matter if you have a social tank, a planted aquascape or a marine reef, using this highly versatile filter material is worthwhile in any case.

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