Every aquarium owner knows the situation: a filter needs to be replaced, but you’re not sure what the best way is to do it. Nobody wants to risk disturbing the filter bacteria because this could endanger the wellbeing of the aquarium dwellers. To say it up front: NEVER seamlessly replace the filter without additional support (we will refer to this next). This could lead to a disturbance of the nitrogen cycle within a few hours and thus result in higher nitrite (NO2) and ammonium (NH4) values, which in the worst case could kill the fish. It doesn’t have to be like this.
It doesn’t have to be like this – the alternatives.
Parallel operation: if possible, operate the old and the new filter together for approx. 10 days. This will ensure that the new filter can “run in” and the old filter can keep up with any necessary tasks.
Transferring the filter media: another option is to place the old filter material into the new filter to transfer the filter bacteria. Some aquarium owners squeeze out the old filter sponge with the sludge into the new filter. This works of course, but it mostly leads to a larger mess. We therefore advise inserting a piece of the run-in filter sponge inside the new filter as a stopgap procedure. This method also works when the device fails completely and parallel operation is not possible.
In case of an emergency
The replacement of a filter is not always planned. A sudden technical fault or leakage can put the filter out of order in an instant. With no fresh water flowing through the filter material for more than 1-2 hours, the filter bacteria die off. This results in a lot of waste-products. To void this, knead the filter material in a bucket of aquarium water to remove coarse dirt. This way the “inactive” sludge doesn’t unnecessarily pollute the water and the remaining bacteria can reproduce within a few hours and days.
In all cases we advise you help the essential filter bacteria to repopulate the filter by adding JBL FilterStart on the new filter materials and also JBL Denitrol to the water column. This will ensure you always have a well-functioning aquarium biotope.