Stream as biofilter - questions

[mjz3348]

I am building a koi pond which will also have a re-circulating stream to act as bio-filter. The stream will be about 50 feet long. Water will be pumped from the pond up to the headwaters of the stream and allowed to flow through the stream bed.

What thickness of filter bed material should I use? I read anywhere from six to 12 inches of "pea gravel". Anyone have experience with this?

The stream bed will be made from a concrete shell which will be hidden with both the filter material and decorative rocks on top. The head of the stream will have a water injection pipe which will have holes along the pipe to inject the water at all levels of the pea gravel. The water will flow down hill and at the other end will be a two drain pipes to gather the water and take it the rest of the way. The drain pipes will have small holes in the bottom increasing in diamter towards the top. In this way water is forced to flow through the entire pea gravel column before exiting the system.

The pond/stream is designed to allow rain water to mix in with the stream water to slowly change over the pond water with rain events.

The pond is over 10,000 gallons in size.

Thanks for any insights

 

[DrCase]

i just wonder how you are going to flush your filter out..when it comes time to clean it..

 

[mjz3348]

I am plumbing it with two drain lines at the lowest end of the filter basin. The drain lines bypass the pond into the storm sewer. Once a year I expect to shut down the filter, open the drain line and let all of the water out introducing air into the system. I'll stir up the pea gravel if I have to.

 

[DrCase]

i had a stream ponds ago..it was hard to keep the water on top of the rocks if it had to much fall.....i wonder if larger river rock would give you more space to collect goop...send us some pics

 

[jessjane]

i just wonder how you are going to flush your filter out..when it comes time to clean it..

It must be take 30 minutes to flow out. How much bigger your drain system of your pond?