The filter foams inside your pond filter have two very important functions and should be treated with care.  The 1st function is to physically screen out large debris such as leaf litter, fish waste and other detritus to prevent this from returning to the pond.  The second function is to act as a housing for beneficial bacteria which break down nutrient in your pond, helping to keep the pond water and its inhabitants in a healthy condition.  You might think that a pristine filter sponge is ideal but in fact, some of the unsightly green slime and muck is actually your friend! The good bacteria can take several weeks to breed on the filter sponges and rinsing all of this off is a step backwards.Many modern pond filters have cleaning functions which greatly reduce the need to touch the foams, partly to prevent getting in a slimy mess but mostly to try to maintain the good bacteria.  This is usually in the form of pull levers which squeeze the foams without having to remove the foam itself. Filtration systems such as the OASE FiltoMatic actually clean themselves!If you must physically handle the foams (perhaps during a major clean down or if your filter does not have easy-clean functions), the best way to clean your filter foams is to gently squeeze out the muck in a bucket of your actual pond water.  Don’t use tap water as this contains chlorine which will kill off the bacteria. Likewise, rainwater may also create a problem as the water chemistry is likely to be different to your pond water. A filter sponge will work best when it is partially clogged so the foam does not need to be pristine by any means.  One of our long-standing customers visited many years back and proudly announced that he put the foams in his washing machine – much to the shock and dismay of his wife stood next to him and was the last to hear the news! Sparkling-fresh the foams may have been but once informed of the best ways to clean the foams, he now enjoys a clearer pond (and fresher clothes).Once the foams have been cleaned, additional bacteria can be added into the pond in the form of a liquid or granular treatment such as BioKick or Viresco.  This bacteria will accelerate the breeding process which would otherwise take 2-6 weeks to establish naturally.  If you own an ultraviolet clarifier, we recommend switching this off for a few days (but leave the pump running) as the UV radiation will otherwise kill off some of the bacteria in the treatment.  The pump will circulate the bacteria which will settle in the pond and in the filter, so the UV can then be switched back on after this period.Filter foams can last many years if cared for but if you notice any signs of deterioration, its best to replace these.  We generally suggest changing these once every 2-4 years and always use the manufacturer’s own branded filter foams as these have been designed and developed over many years to ensure maximum efficiency.  A knock-off bath sponge will not offer the same level of filtration!If you need any advice on your pond filter, get in touch with one of our friendly technical assistants.