Oh good, this is an easy one . Buy two filter socks appropriately sized. Hook one up to the bottom of your overflow tube and store the other. When the filter sock gets full of detritus, take it off, put the clean one on. Then wash the dirty one either in your dishwasher with regular dish soap, or in your washing machine with bleach only
You'll have to hang the sock from something so that the ridge of the sock is just above the water level to catch the bubbles. The sock shouldn't overflow but if you do hang it right, it can only overflow into th tank