Just like with an undergravel filter, it’s the lack of proper maintenance that causes bio balls to produce nitrates. If you periodically rinse bio balls and keep them clean, nitrate problems should decrease, as long as this is the only source of nitrate problems in the aquarium.
How to clean bio balls:
- Place some new saltwater in a five gallon plastic bucket, or similar container. This is where you will rinse and clean the bio-balls off. If you are planning a water change, water removed from the aquarium can be used.
- Turn off the filter.
- Remove about 1/4 of the bio-balls from the filter chamber and place them into the container with the saltwater.
- Stir and swish the bio-balls around in the saltwater to break all the gunk or organic matter loose that is stuck on them. If they are extremely dirty, you may have to repeat this step. DO NOT scrub the bio-balls! Just allow the saltwater to do the job, nothing more than that.
- Scoop the rinsed bio-balls out and place them back into the filter bio-chamber. A plastic kitchen colander works great for this, but any type of cup or small container with drain holes in it will do. The bio-balls come out, the dirty water stays behind.
- Restart the filter.
- Test for the appearance of ammonia every few days for a week, then every several days over another week after that. If the tests read near zero after this time, it’s OK to repeat the process with another 1/4 of the bio balls. If ammonia does appear, wait until readings drop back to zero, then wait another couple of weeks after that before repeating the process with the next batch of bio-balls.