This is an easy to service filter and filter media is readily available from various pond suppliers. A bit small for the size pond we have but works well in fall through winter. Need to service more often in late spring and through out summer. Best to purchase 2 so you can rotate one out and service the other when convenient. Typically service about every 3-4 weeks for our pond (est 3000 Ga). Have tried to purchase additional filters but Great Offer Stock no longer carries them.