The Juwel active carbon sponge cleans the aquarium water of all chemical impurities by absorbing them in its active carbon. Consequently, these chemical impurities will not effect the bacteria - cultures inside the blue sponges. If the carbon sponge is left in the filter too long, it can release the chemicals again into the water.
- Johan M. wrote about Juwel bioCarb -active carbon sponge- in 2015:
Effectively resorbs bacteria/bad odour. Now and then you will have, for example, a dead fish in the aquarium. Recommended!