Ouch. I don't have a bog filter as such, but when I was starting out I tried a filter system that was a large container filled with pea gravel and river bed stone as one of my experiments. The set up worked fine for a while then I noticed the water was flowing up in little chimneys that had formed throughout the rock. Except for the chimneys the rock was solidly packed with mulm. Slowly the filtration effect stopped. I think this is what has happened to your bog. It stank to high heaven when I turned off the water flow to clean it . It was almost impossible to clean. I've been leery of rocks on the bottom or in filters ever since.

I finally wound up with a Skippy which doesn't use stones.I clean it once in the spring and once in the fall unless the raccoons dump plants, pots and all into the water. It has a cleanout valve.

I looked at a lot of sites before giving you any info from my great lack of experience. There was a consensus that bog filters must be cleaned regularly. Without the regular cleaning the problem you have would develop.

There were a number of examples of a system of tubes with a cleanout tap in most. Some worked with a backflush which I would avoid due to the likelihood of contaminating the pond with anaerobic bacteria. Most suggested 12 to 14 inch depth of stones. A couple used bottom drains or a combination of methods.There was good info in others though if only what to avoid and the consequences of not cleaning. I think the search term I used was "bog filters+ ponds" Likely you will get similar sites with your search engine. The one that was most interesting is off limits on GW due to advertising problems.

We have had a few posters who put in bog filters but they haven't posted in a while. Maybe they will show up with their much, much more extensive experience. At least I haven't heard anything negative from them about bog filtration.

Let me know what you think. I was considering trying again. I hate to say it but it sounds like you may need a backhoe. The thought of three feet of contaminated rock would have me thinking about a lawyer. You would need to be very cautious since the gases that get released are dangerous, sometimes deadly. You hear about people dying while cleaning out septic systems by hand and really, that is what you have at the moment, a closed septic system. If you have respiratory problems you will have to hire someone. In any case with the amount of packed mulm you have, a respirator at least seems advisable. Forget a shovel.

I completely agree w/ Sandy. I definitely think you need a different media and need to be careful removing it.

I sent you an email - just noticed it's visible.

This post was edited by ademink on Mon, Jul 22, 13 at 11:29

I agree with everything Sleepless said. I built a bog on a previous pond and was very pleased with it's performance for the first two years. After that it was useless. I removed it and as was said found that the gravel was completely clogged with mulm. The concept is great and works well in nature but isn't suitable for most pond situations. As was mentioned you can install an elaborate cleanout system but it will be costly and still take a lot of maintenance. There are a lot more efficient filtering systems available, even DIY, that will do a much better job and take up much less space.

My pond is 1100 Gallons, about 20 times smaller than yours but I think they scale. You obviously have a pump that can handle sufficient water volume to be able to filter your water. I use a 55 gallon food quality plastic barrel as an upflow filter. I have seen on line several designs where 2 to 5 barrels are daisy chained to provide the filtration. If you look, I think you can find some DIY designs that you can do fairly inexpensively. I think my filter cost about $100 excluding the sprinflo bioribbon which I have since discovered is not much different from the PVC strapping you can buy in a store or on-line for packaging. The rest of the material you can get from Home Depot or any plumping supply store pretty cheap.

I agree with the others. A basic skippy biological filter works great for me.

I have included the link below to my pictures of the build. The pipe outlet doesn't work - it can get clogged and the filter overflows and you have an empty pond. I plan to change it to a waterfall type. Also our silicone gaskets didn't work. We went back and used marine epoxy which has lasted for a number of years.

You can also check The World Famous Skippy Page.
http://www.skippysstuff.com/biofiltr.htm

You can spend hundreds on a commercial biological filter, but a home-made skippy filter works great for many people and is easy to build. Mine cost $75 including the tank, filters material, piping, and misc stuff and lots of trips to Lowe's. Yours would cost more for a bigger tank unless you used garbage cans linked together. There are some posts about that here too. Just search for skippy and you'll find a lot of information.

Good luck. Let us know what you came up with.

Here is a link that might be useful: Pashta's Skippy Filter