Chemical pond filtration uses a chosen medium to remove particular dissolved substances. It is a supplement for a defined problem, not a replacement for mechanical waste removal and biological ammonia processing. It does not automatically halt the nitrogen cycle.
Activated Carbon
Activated carbon adsorbs many dissolved organic compounds and can help with some odors, discoloration, or removal of certain treatments when their instructions call for it. Ordinary activated carbon should not be relied on to remove ammonia in a freshwater koi pond.
Its usefulness depends on the substance, contact time, water conditions, and remaining capacity. Replace it according to the application and supplier's directions. A routine ammonia test does not tell you that carbon has reached its capacity for every organic compound.
Zeolite
Suitable zeolite media can bind ammonium in freshwater. It may provide temporary support in some situations, but capacity is finite and it can obscure whether a young biofilter can handle the fish load. Keep testing ammonia and nitrite.
Salt can interfere with ammonium-binding media and can cause release from some zeolites. Do not combine zeolite with salting or regeneration in a live fish system without checking the product instructions. Any permitted regeneration belongs in a separate container, followed by the manufacturer's preparation steps.
Use Media for a Specific Job
- Identify the substance or problem you are trying to manage.
- Check that the chosen product is designed for that use.
- Provide the stated flow and contact conditions.
- Monitor the relevant water tests and record replacement dates.
- Correct the underlying waste, stocking, or filtration issue.
Remove or bypass carbon during a medication only when the treatment instructions require it; it can remove some active ingredients. For persistent ammonia, investigate the biological filter rather than continually adding media.
Compare all three functions in the pond-filtration guide.