Everything You Need to Know to Build the Perfect Backyard Pond

One type keeps water free of debris so that the pump won't clog. The other removes chemicals that harm fish. To sustain fish, you'll need both types or a product that puts both in one package.

Mechanical
Traps debris before it reaches the pump. Clean weekly in spring and fall, every other week in summer, monthly in winter. A filter in a waterfall or a surface skimmer will be easier to reach than one on a pump at the bottom.
$60—$800. PondScapeOnline

Biological
A must for ponds with fish. Bacteria living on a porous medium digest toxic nitrites and ammonia. Wait six to eight weeks for them to become established, or buy a starter colony. No cleaning needed.
$140—$500.