Hi Alicia!

The rule of thumb for larger koi ponds (10000 gallons and up) is enough pump flow to put about 1/2 to 3/4 of your water through your filters every hour. Smaller ponds require higher throughput, that is, every molecule of water in your system exposed to the filter media once an hour.

Remember that what the pump's label advertises is not what you are putting through the system. Every foot of elevation above grade added to every foot of pipe and every turn your piping makes adds to your head loss and decreases your flow. Our website's home page has a series of links to tables that will help you calculate how much flow you are losing from these sources of resistance. It should help you upgrade your system.

Please note that your problems with algae and debris may not be your pump's fault. Algae is the product of sunlight, temperature, ammonia and phosphate. You will reduce the algae load some by improving your filter throughput and reducing your ammonia load, but only to a point. You may want to set up a whole new filter system in parallel to your existing setup to increase your pond's bioconversion efficiency. Floating (microscopic) algae can be controlled with UV. Hair (or string) algae is best handled with nutrient and sun restriction and control of ammonia. Excess algae can be removed with a toilet brush on a broomstick. Avoid algaecides.

The debris problem has many sources. Outside debris can be partially cleared with a skimmer setup. Large suspended solids require a pre-filter or a vortex. Bottom debris resolves with removal of all that rock on the bottom of your pond and installation of a bottom drain.

Ponding is fun. There's always another challenge.

Bob