Dirty or cloudy aquarium water caused by fish waste, decaying organic material and particles of food should be treated quickly to prevent the spread of disease. Filter Wool has a fine web of fibres and is very effective at trapping the fine particles that spoil water clarity, whilst not effecting the water chemistry. Supa Filter Wool is ideal for use in many types of freshwater and marine aquarium filters including all external canister filters, box and trickle filters.