When designing your pond, you will probably hear about both gravity and pump fed filters. So let's talk about what these two approaches offer.
A pump fed design is when the water is pulled out of the pond and fed into the filter, then pushed back into the pond via gravity or another pump. If you look at the market, over 90% of ponds are built using a pump fed methodology. This is mainly driven by the fact it's faster to build (and easier) to get running. The pump can be submerged directly into the pond without requiring any drain or "holes" in the liner (although you can also use a bottom drain - more to come on that subject).
The process of bringing the water AND the waste is dependent on the pump. The pump's ability to push water to the filter depends on where the pump resides (that is where head pressure comes in). Additionally, the waste gets broken up by the pump and makes it harder for the mechanical filter to separate since it enters the filter as a fine mess. This fine mess can clog screens and filters and allow more waste to enter the biological filter than desired.
A gravity fed system relies on gravity to bring water to the filter and a pump then takes the water from the filter back to the pond. This adds a bit of a challenge since the water level of the pond and the water level in your filters need to be the same and typically implies more work during the initial building. It also can add more to the budget because of the additional plumbing needed. The ideal way to do this is using a bottom drain.
The big benefit of a gravity fed pond is that the fish waste is delivered to the filter in-tact. This makes it easier for your filters to get rid of the waste sooner in the process which means your filters can do more to keep the water clean. On thing to add is that the water flow is based on the size of the drains, not the size of the pump.
Both designs work and both have pros and cons. For the serious Koi Keeper who needs to handle large fish waste and wants to ensure that the water is clean, its worth understanding these two approaches. My current pond is a pump fed design (with bottom drains). I'm looking to see whether to add more mechanical filters to help with the fine mess OR whether to switch to a gravity fed system and gain the benefits of that approach.
Interested in your opinion. Please share what your pond is using and what your experience has been!
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