How to Use Activated Carbon in Your Aquarium

Blessings Aquarium
Jul 10
2 min read

Activated carbon is one of the most trusted filtration media in the aquarium hobby. Whether you’re a beginner or an experienced aquarist, learning how to use activated carbon in your aquarium can greatly improve water clarity and fish health. In this blog, we’ll explore what activated carbon is, how it works, when and how to use it, and some important tips to make the most of it.

What Is Activated Carbon?

Activated carbon is a highly porous form of carbon that’s specially treated to increase its surface area. This makes it extremely effective at removing impurities from water. It’s

commonly used in chemical filtration for both freshwater and saltwater aquariums.

What Does Activated Carbon Remove?

Activated carbon removes:

Chlorine and chloramine
Organic compounds (like fish waste and uneaten food)
Odours and discoloration
Medication residues (after treatment)
Tannins released by driftwood

However, it does not remove ammonia, nitrites, nitrates, or heavy metals.

Why Should You Use Activated Carbon in Your Aquarium?

Here are a few reasons to include activated carbon in your aquarium filtration:

Crystal Clear Water: Removes yellowing compounds and makes water visibly clearer.
Odour Control: Eliminates unpleasant smells.
Improved Fish Health: Reduces organic waste that can stress fish.
Medication Cleanup: Helps remove leftover chemicals after treatment.
Aquascaping Support: Removes tannins from driftwood, keeping water colour stable.

Where to Place Activated Carbon in Your Aquarium Filter?

Activated carbon should be placed in the last stage of your filter media setup, after mechanical and biological filtration. This allows clean water to pass through it for maximum efficiency.

👉 For canister filters, place it in the top tray.

👉 For internal or hang-on-back (HOB) filters, place it in a mesh bag inside the filter compartment.

How Much Activated Carbon Should You Use?

A general rule:1 tablespoon per 10 gallons (38 liters) of water.

However, high-bioload tanks (like monster fish tanks or goldfish tanks) may require more.

Always read the manufacturer’s recommendation on the packaging.

How Often Should You Replace Activated Carbon?

Activated carbon becomes saturated over time and stops working. Replace it:

Every 3–4 weeks in most freshwater tanks
Every 2–3 weeks in heavily stocked or planted aquariums
After any medication treatment

⚠️ Don’t wash and reuse activated carbon – it’s a single-use product.

Can Activated Carbon Harm Aquarium Fish?

No, if used correctly. But:

Don’t use it while dosing medication — it will absorb the medicine.
Don’t place it directly near air stones or in turbulent flow areas, as it may break down.
Always rinse it thoroughly before use to remove fine dust.

Are There Alternatives to Activated Carbon?

Yes, depending on your tank’s needs:

Purigen – for long-term polishing
Zeolite – for ammonia removal
Resin-based media – for specific toxins

However, activated carbon remains the most affordable and versatile option for most aquarium setups.

Is Activated Carbon Right for Your Aquarium?

Absolutely! If your goal is to maintain clean, odor-free, and crystal-clear water, activated carbon is a must-have. It’s easy to use, effective, and suitable for a variety of tanks — from nano aquariums to large monster tanks.

At Blessings Aquarium, Pune, we stock high-quality activated carbon and other essential aquarium supplies. Visit our gallery or shop online to explore the best filters, media, and fish care products.