Despite our best efforts to maintain equipment, it inevitably needs to be replaced from time to time, including filters. Even if the filter is still in prime condition, sometimes you just want to upgrade to a newer model. Replacing a filter is not difficult but it can be disruptive to the biology crucial to keeping your aquarium healthy. Although good nitrifying bacteria live throughout your aquarium, the population is concentrated in the bio media in your filter.
If you disturb your bacteria population, you can cause New Tank Syndrome (NTS), which is marked by a cloudy aquarium and dangerously high ammonia. Here, we’ll go over the best practices for installing a new filter to maintain a stable aquarium and avoid NTS.
Regardless of how you transition between filters, you should not do a water change at the same time to avoid removing too much bacteria. Instead, do a slightly larger water change the week before (no more than 30%) and feed sparingly to keep the waste low. Hang on to your bio media if you can and do not wash it so that you can preserve the bacteria colonies from your old filter.