AquaForte Dirty Harry In-Line Pre FilterProduct Description The pre filter ensures that larger waste solids in the pond water, such as leaves, small branches and larger algae particles are collected before they are caught up in the pump or in the filter. By pre filtering the water, you prevent larger particles from clogging up or overloading the filter. The service life of the pond pump is protected because large particles will not damage the impeller of the pump. The housing of the pre