Review on Maximizing Filtration Performance with Dennerle Filter Element: The Ultimate Aquatic Solution by Mohan Joseph

I like this filter and these refills are good. But I won't buy it again because it's too expensive. I kept the frame from the replacement unit and simply cut a piece of filter cloth that I bought in bulk and inserted into the frame. This filter does not contain activated carbon. I also replaced the sponge on the bottom with a carbon sponge. This German filter is worth the money. You don't hear anything and you can control the flow of water. The slow flow setting is ideal for betta fish.