Bogs as Fish Filters

by Jeff
(Jupiter, Florida)

I am building a Koi pond and want to send the fish waste into a bog. How do I build this type of bog? and Will the clean water from the bog be able to go back into the pond?

Doug says that yes, this is a viable solution.

The specific answer to your question however is that yes you can do it - but the size of the bog is determined by the size of the pond and the fish load it's expected to carry. You're creating a filter system and the flow rates have to be calculated fairly well or you'll wind up with problems.

In general bogs should be approximately 20% or greater the size of the pond for an "average" pond. If the fish load is to be higher than the recommended 1-2 inches of fish per square foot of water, then you're going to have to increase the size of the bog to handle this load. I'm afraid I can't give you this factor but with the high heat of Florida, I wouldn't be adding too many fish past safe limits unless you have plans for backup power (any power outage takes out your pumps and fish start dying quickly).

The single most important thing to remember in making a filter-bog is to put a drainage hole/valve on the bottom so you can drain it and clean it out at some point. Without this, you're going to wind up with problems at some future date if/when the pond gets out of whack somehow and your filter is old and needs rebuilding. You really will thank yourself for building this into the system.

Hope this helps