After three months of use, I found the charcoal cartridges are very effective but do not rely avoid changing very often. With 25 liters and four small juvenile guppies, a regular maintenance of the aquarium with suction bottom of the waste, I have to change the cartridge every 3-4 weeks to keep up a clear water. Unlike the "foam" cartridges, it is useless and vain to rinse Tetra pack cartridges, change the ... Dennerle filter cartridge is more expensive to purchase that is true, but it can be rinsed at least 5 or 6 times before changing it. So make its accounts ... If it again, I fit out my two filter trays Dennerle, more expensive but more efficient. Fortunately 2 euros Tetra cartridge, it is reasonable to have a crystalline aquarium and odorless.
