Now is the time to clean out your pond bio-filter
So we are well into 2006, and coming to the end of January when you should be thinking right now about cleaning your pond bio-filter, because in winter here in England the temperatures are still low enough that any bacteria on the media in the bio filter will still either be dead, or very low activity. Therefore you won't be disrupting the filter too much if you decide to take your bio-filter apart and give it a good clean out. You should still really only clean the filter media in a bucket of pond water, so as to leave at least some bacterial residue on it. Don't use tap water on the filter media because the chlorine will kill off everything.
For my homemade design of bio-filter I usually give it a once-a-year cleanout, at the very start of the year, by totally dismantling it, removing all filter media and giving a good clean, fixing any problems and making good any pipe connections which look as though they might cause problems and so forth. Because I start to do this very early in the year it means the bio-filter can build up the bacteria again as the warmer weather comes, and so it is ready for the summer months. This is much better than leaving it until later in the year after it has built up the important bacteria because cleaning it then may kill-off the bacteria and that might lead to problems with green water in the pond.
Once this big clean up has been done I then resort back to the usual cleaning and maintenance cycle as detailed on my pond bio-filter website.