Acurel Ammonia Reducing Media Pads are durable polyfiber pads infused with special ammonia-absorbing particles to pull ammonia from aquarium or pond water. Ammonia, the leading killer of tropical fish, is the result of fish waste and decomposing food in the aquarium. To be used as a preventative measure - not a remedy for sustained ammonia concentrations. This thicker, more rigid design performs better than other media pads. For use in all fresh water aquariums and ponds.