Activated carbon is a popular filtration media found in the aquariums hobby due to its ability to improve water quality. Here are the key benefits of using activated carbon in your aquarium:
1. Removes Toxins & Impurities
Activated carbon effectively absorbs organic pollutants, chemicals, and toxins, keeping the water clean and safe for fish and other aquatic life.
2. Eliminates Odors
It helps remove foul smells caused by decomposing organic matter, uneaten food, and waste, keeping the tank smelling fresh.
3. Clears Up Water
By adsorbing dissolved organic compounds, activated carbon reduces discoloration and cloudiness, making the water crystal clear.
4. Removes Medications & Heavy Metals
After treating fish with medications, activated carbon can help remove any residual chemicals from the water, preventing unwanted buildup. It also helps in filtering out heavy metals like chlorine and chloramine from tap water.
5. Reduces Yellowing from Tannins
For those using driftwood or botanicals, activated carbon helps counteract excessive tannins, preventing the water from turning too dark or acidic.
Now while activated carbon has many benefits to your aquarium, there are some drawbacks to consider when using it in your aquarium:
1. Removes Beneficial Elements
Activated carbon can absorb essential nutrients, such as trace minerals and fertilizers, which are important for planted tanks. It may also reduce beneficial tannins from driftwood and botanicals that some fish and shrimp species rely on.
2. Needs Frequent Replacement
Once saturated, activated carbon stops working and can even start leaching absorbed toxins back into the water. It typically needs to be replaced every 2-4 weeks, adding to ongoing maintenance costs.
3. Does Not Remove Ammonia, Nitrites, or Nitrates
Unlike biological filtration, activated carbon does not break down harmful ammonia, nitrites, or nitrates, which are the primary causes of poor water quality in fish tanks. A proper biofilter is still necessary to maintain a healthy aquarium.
4. Can Remove Medications
If used during fish treatment, activated carbon can absorb medications from the water, making them ineffective. It must be removed when dosing antibiotics or other treatments.
5. May Release Phosphates
Some lower-quality activated carbon may leach phosphates into the water, which can lead to excessive algae growth. Using high-quality, phosphate-free carbon helps avoid this issue.
6. Can Be Messy if Not Rinsed Properly
Activated carbon dust can cloud the water if not thoroughly rinsed before use. Fine particles may also escape into the tank, which can irritate fish and clog filters.
We alway recommend running either filter sponge or ceramic rings/balls in your HOB (hang on the back) filter alongside your activated carbon cartridge. This ensures that beneficial bacteria have a stable home, preventing a loss of biological filtration when you replace the carbon cartridge.
Why?
1. Activated carbon does not support beneficial bacteria – It primarily absorbs chemicals and toxins but offers little surface area for bacterial to populate.
2. Cartridge replacement removes bacteria – Many carbon filter cartridges contain mechanical media that traps debris, and when you replace them, you lose both mechanical filtration and beneficial bacteria that may have started growing on them.
3. Sponge or ceramic media provides a permanent home for bacteria – These materials do not need frequent replacement ( 6 months to a year) and serve as a long-term biological filtration base.
when you strictly rely on just the carbon cartridge in your filter you risk disrupting your aquarium’s nitrogen cycle and Here’s what could happen:
1. Loss of Beneficial Bacteria
Most of your beneficial bacteria live in your filter media (especially in sponge and ceramic media). When you replace the cartridge, you’re removing a large portion of your bacterial colony, leading to a potential mini-cycle where ammonia and nitrites spike.
2. Ammonia & Nitrite Spikes
Without stable biological filtration, your tank depends on bacteria growing on the cartridge to process fish waste. When you remove it, the new cartridge has no bacteria, forcing your tank to re-establish its bacterial population every time, leading to temporary ammonia or nitrite spikes.
3. Poor Water Stability & Cloudiness
Frequent filter cartridge changes disrupt the balance in your tank, which can cause:
• Cloudy water
• Stress to fish
• Increased algae growth due to fluctuating nutrients
• Bacteria blooms
4. Increased Maintenance & Stress for Fish
Without a stable biological base, you may need to do more frequent water changes to compensate for bacteria loss. Your fish may experience stress or illness due to unstable water parameters. Ich is an opportunistic parasite that often appears when fish are stressed due to sudden water parameter changes. If ammonia/nitrites rise due to bacteria loss, fish become weaker, and ich outbreaks are more likely.