Pond Medic Biological Filters are gravity fed filterS and come with various filter media as well as a UV sterilizer.
There are 3 models
COMBO 1:8W UV,3000L POND CAPACITY,MAX FLOW 1500-2500L/H
COMBO 2:8W UV,5000L POND CAPACITY,MAX FLOW 2500-4000L/H
COMBO 3:8W UV,7500L POND CAPACITY,MAX FLOW 3500-6000L/H