Can a bio-filter in winter be boosted with bacteria from a tropical fish tank?
The bacteria in a freshwater tropical fish tank filter are the same as those in a Koi pond bio-filter, (Nitrosomonas & Nitrobacter), but in winter, trying to seed the pond filter with their cousins from a tropical tank will not help. In winter, the Koi pond’s bio-filter bugs are either dormant or have a very low metabolic rate, waiting for warmer weather. As the water warms, they slowly increase their metabolic rate and begin to “eat” Ammonia (and Nitrite), just as they did the previous summer, but they will only do this at a rate that is controlled by the water temperature. If the tropical fish tank is in the usual temperature range of 20oC or higher, the filter bugs will be active in its filter, but as soon as they are put into the cold water of a Koi pond bio-filter in winter, they too will become dormant. Bug activity is dependent on temperature so feeding fish very sparingly with low protein food until the water is warm enough for the bugs to have recovered their full colony size
