Instructions
Decide whether to go with an up-flow or a down-flow type filter. Both rely on gravity to get the debris to the bottom of the pool; the difference lies in how they distribute the water back into the koi pond. The main drawback to a down-flow filter is that it tends to plug up over time as sediment builds up in it. The main drawback to an up-flow is that it isn't as effective as the down-flow at cleaning. So, you have to decide which is more important to you.
Get the right size for the job. No matter what kind of filter you get, you need to pay attention to the GPH (gallons per hour) rating. Your pond should be filtered completely every one to two hours, so look for a filter that's up to the job.
Check out the price tag. A good gravity-flow filter is an investment, but that doesn't mean you can't shop around for the best deal. Free shipping always sweetens the deal, and often times local companies may come out and help you install it at no additional charge. So crunch the numbers before buying.
Read the label. Many filters come with special features like UV lights or pre-seeded with bacteria, so find out what features each filter has before deciding on the perfect one for your koi pond.
How to Buy Gravity-Flow Filters for a Koi Pond
Choosing the right filtration system is one of the most important decisions you'll make for your koi pond. Gravity-flow filters are one of the most popular types of filters on the market and rely on gravity to bring the waste products to the bottom of the pond. The filter then vacuums it out, runs it through biological media and then pumps it back up to the pond's surface.