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.https://www.aquaristikshop.com/aquaristic/Juwel-bioCarb-active-carbon-sponge/432109/
- 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!