What is the correct way to build a bog?

[fisharefishy99]

I finally got around to building a bog for my pond. I have pretty much finished digging today but I had a few questions about it that I can't quite figure out.

1. How deep should it be? I figured 2 ft should work but if deeper or shallower is better I don't mind.

2. Do I fill it with pea gravel completely? Or do I make a shelf so it is only at the top?

3. How do you clean it? Do you even need to?

4. Should I put a solids settling filter before the bog since I will not be able to put a back flush on the bog? (55 gallon drum upflow skippy filter that has a backflush)

5. Is 2,000 gph an appropriate flow rate for a bog?

Those are my main questions that are coming to mind right now. My pond is 2,000 gallons with a surface area of around 108 square feet, the bog will be 7 ft by 4 ft. My Koi load is going to be on the heavier side since I have a tendency to overstock. I have a serious pea soup algae problem, so a strong performing bog is my number one concern, especially since it will be my only filter.

 

[addy1]

It all depends on who you ask. Some think a bog is old technology and will muck up without cleaning.

The way mine is made:
It is 2.5 deep, mainly because that is how deep I made it, they are fine at 8 to 12 inches. But I figured more gravel better filtering.
I didn't clean our pea gravel, it was a very dry summer and we are on a well. But it has not caused any issues.
I did an up flow with pvc piping below the gravel, pushing water through the gravel, no space between the bottom and the gravel.
I do not clean mine, do have a back flow pipe if I ever need to clean it.
Mine draws water from almost the bottom, but not the bottom. I did not want to suck up snails, tads etc. (Goldfish, shubbies only)

If you are pulling from a bottom drain it wouldn't hurt to have a settlement chamber/solids filter before the bog.

This is a shot at the 5 foot area, I have not cleaned the pond all summer, i.e. netting the bottom, never have green water or string algae. The pebbles on the bottom is spilled pea gravel and some kitty litter. The dark lumps are trap door snails. The black pots are floating lilies

My flow is around 6000k in the bog, the bog is 27ft x 4.5 feet or so. Full of plants. This is its third summer, second with a fish load, and whatever else lives in the pond load.

 

[Waterbug]

There's no specs on bogs that I know of. For example I don't know of anyone ever testing different cogfigurations. Most people will just say "this is how I built mine". But I think you can tweak it for how you want it to work for you and the available space.

1. How deep should it be? I figured 2 ft should work but if deeper or shallower is better I don't mind.

Can be as little as 4-6" or as deep as you like. Factors to consider... Adding plants? In pots? make sure it's deep enough to cover a 15 gal pot I'd say. Because you might want to clean it out some day the more shallow the easier the shoveling. I think really deep bogs don't really use all of the bog. Water will take the shortest path it can and even with complex diffuser piping water with still pretty much go where it wants. So a long bog that's say 1' wide and 6" deep will be more fully utilized than a cube shape.

2. Do I fill it with pea gravel completely? Or do I make a shelf so it is only at the top?

Filled completely. You can choose to almost fill it and even mound gravel in the middle if you like for some plants. Don't know what you mean by a shelf.

3. How do you clean it? Do you even need to?

Generally they are never cleaned, but that's your choice on what you want. Initially when clean a bog is a very good bio filter. As muck collects its function as a bio filter decreases. As collected muck breaks down it releases DOC and other less than good things into the water. At some point all the open space in the gravel will be filled with muck and water will only run across the surface. Plants will love that but the plants will pull virtually all food from the muck, not the water, so little filtering.

Has to be your call on what point you wanted to clean it. They all fill with muck at different rates, so there's no set time period. Bur in general...If you wanted it to act as a bio filter you might have to clean it every few days so you'd want to design something easy to clean. When run like that it would be more of a gravel filter which people used years ago and stopped because cleaning was hard. If you wanted it to act as a veggie filter you could clean it a couple of times a year.

But I'd say the basic concept of a bog is that it's never cleaned. It can take 3, 5,10, 15 years for one to completely fill with muck. So most people running bogs have never had the experience. People move, design the pond, etc., before the bog is clogged.

4. Should I put a solids settling filter before the bog since I will not be able to put a back flush on the bog? (55 gallon drum upflow skippy filter that has a backflush)

Any organic matter you stop from going into a bog is going to increase the time before it clogs.

Backflushing a bog isn't really possible. At best you can drain out some dirty water. For any filter to actually backflush the media has to be bounced around to break up the clogs. Not really possible with gravel on the scale of a bog.

5. Is 2,000 gph an appropriate flow rate for a bog?

Depends on the bog. However most bogs can take a huge flow because there are no pipe restrictions, assuming the bog overflows into the pond. You only have to make sure the overflow is wide and deep enough. But pretty easy to make that handle 10,000, 20,000, 50,000 GPH ...huge. There can be issues with water running across the top of the gravel depending on the shape of the bog, flow and location of in and outputs however. But it still "works".

Those are my main questions that are coming to mind right now. My pond is 2,000 gallons with a surface area of around 108 square feet, the bog will be 7 ft by 4 ft. My Koi load is going to be on the heavier side since I have a tendency to overstock. I have a serious pea soup algae problem, so a strong performing bog is my number one concern, especially since it will be my only filter.

That could be a problem. Bogs are great filters on the right pond. Lighter the fish load the more a appropriate a bog. Most light fish load ponds don't require any bio filter, the pond pipes, etc., are enough. Heavier the fish loads the more bio filtering is needed to keep fish alive. And every range in between.

I don't know what your fish load actually is so no idea on what you might need. When someone says 2000 gal, followed by Koi, followed by heavy...I start to think a serious filter system might be needed.

BTW, I'm not sure if you know this or not but the algae making the green water consume ammonia directly, so you probably have zero ammonia, and very low nitrate too. The algae is your current bio filter, and it's a very good bio filter. If you do anything to clear the water you might want to test ammonia often, like everyday, for awhile to make sure you don't have trouble.

 

[fisharefishy99]

It all depends on who you ask. Some think a bog is old technology and will muck up without cleaning. The way mine is made: It is 2.5 deep, mainly because that is how deep I made it, they are fine at 8 to 12 inches. But I figured more gravel better filtering. I didn't clean our pea gravel, it was a very dry summer and we are on a well. But it has not caused any issues. I did an up flow with pvc piping below the gravel, pushing water through the gravel, no space between the bottom and the gravel. I do not clean mine, do have a back flow pipe if I ever need to clean it. Mine draws water from almost the bottom, but not the bottom. I did not want to suck up snails, tads etc. (Goldfish, shubbies only) If you are pulling from a bottom drain it wouldn't hurt to have a settlement chamber/solids filter before the bog. This is a shot at the 5 foot area, I have not cleaned the pond all summer, i.e. netting the bottom, never have green water or string algae. The pebbles on the bottom is spilled pea gravel and some kitty litter. The dark lumps are trap door snails. The black pots are floating lilies

My flow is around 6000k in the bog, the bog is 27ft x 4.5 feet or so. Full of plants. This is its third summer, second with a fish load, and whatever else lives in the pond load.

I think I'm going to follow the same design you made as far as how to layout the pipe and the upflow, I found a post where you put pictures on how to make the PVC diffuser that was very helpful

That water is incredibly clear by the way! Plus that pond looks awesome!

There's no specs on bogs that I know of. For example I don't know of anyone ever testing different cogfigurations. Most people will just say "this is how I built mine". But I think you can tweak it for how you want it to work for you and the available space. Can be as little as 4-6" or as deep as you like. Factors to consider... Adding plants? In pots? make sure it's deep enough to cover a 15 gal pot I'd say. Because you might want to clean it out some day the more shallow the easier the shoveling. I think really deep bogs don't really use all of the bog. Water will take the shortest path it can and even with complex diffuser piping water with still pretty much go where it wants. So a long bog that's say 1' wide and 6" deep will be more fully utilized than a cube shape. Filled completely. You can choose to almost fill it and even mound gravel in the middle if you like for some plants. Don't know what you mean by a shelf. Generally they are never cleaned, but that's your choice on what you want. Initially when clean a bog is a very good bio filter. As muck collects its function as a bio filter decreases. As collected muck breaks down it releases DOC and other less than good things into the water. At some point all the open space in the gravel will be filled with muck and water will only run across the surface. Plants will love that but the plants will pull virtually all food from the muck, not the water, so little filtering. Has to be your call on what point you wanted to clean it. They all fill with muck at different rates, so there's no set time period. Bur in general...If you wanted it to act as a bio filter you might have to clean it every few days so you'd want to design something easy to clean. When run like that it would be more of a gravel filter which people used years ago and stopped because cleaning was hard. If you wanted it to act as a veggie filter you could clean it a couple of times a year. But I'd say the basic concept of a bog is that it's never cleaned. It can take 3, 5,10, 15 years for one to completely fill with muck. So most people running bogs have never had the experience. People move, design the pond, etc., before the bog is clogged. Any organic matter you stop from going into a bog is going to increase the time before it clogs. Backflushing a bog isn't really possible. At best you can drain out some dirty water. For any filter to actually backflush the media has to be bounced around to break up the clogs. Not really possible with gravel on the scale of a bog. Depends on the bog. However most bogs can take a huge flow because there are no pipe restrictions, assuming the bog overflows into the pond. You only have to make sure the overflow is wide and deep enough. But pretty easy to make that handle 10,000, 20,000, 50,000 GPH ...huge. There can be issues with water running across the top of the gravel depending on the shape of the bog, flow and location of in and outputs however. But it still "works". That could be a problem. Bogs are great filters on the right pond. Lighter the fish load the more a appropriate a bog. Most light fish load ponds don't require any bio filter, the pond pipes, etc., are enough. Heavier the fish loads the more bio filtering is needed to keep fish alive. And every range in between. I don't know what your fish load actually is so no idea on what you might need. When someone says 2000 gal, followed by Koi, followed by heavy...I start to think a serious filter system might be needed. BTW, I'm not sure if you know this or not but the algae making the green water consume ammonia directly, so you probably have zero ammonia, and very low nitrate too. The algae is your current bio filter, and it's a very good bio filter. If you do anything to clear the water you might want to test ammonia often, like everyday, for awhile to make sure you don't have trouble.

Answering in order of the questions I asked originally, if that makes sense haha.

1. Okay perfect, I think two feet should allow me to dig the plants in deep enough and make shoveling not too ridiculously hard. I agree that a deeper bog than that would likely be not that much more beneficial.

2. I like the idea of making mounds because I would like a small area to have little to no pea gravel, maybe like 3/4 of the bog filled to the top with pea gravel and a 1/4 of it open water. Just so I can put some floaters in and possibly add some matala mat that I have left over. What I meant by shelf is like a permeable grate that keeps the pea gravel away from the bottom. I saw in a video a guy who made a bog that was about two feet deep and the gravel was held up by a shelf with legs that made it only so the top couple of inches had gravel and below it was just open water.

3. Interesting... so it basically only acts like an "all in one" filter for a little while then it loses it's bio filter capabilities rapidly. But it can remain a mechanical filter for years without cleaning is what I am understanding. What if I filled part of it up with matala mats? Would those help at all with bio filtering? I have a bunch left over from my 55 gallon drum filter. Not sure how I would implement them though.

4. I looked at the design and realized it would be next to impossible to run the 55 gallon drum prior to the bog, the best I could do is MAYBE run them in parallel. Too bad because it sounds like I would have been able to keep it efficient a lot longer. I wonder if a pressure washer might be able to deep clean the bog at all, that combined with a sump pump.

5. Okay perfect, I need as strong a flow as possible.

I took a video so you can see the fish load. This is about every fish in my pond except maybe one or two, they are all pretty good about coming for feeding time. I also have four turtles, not sure how much they add to the load but I bet it's at least as much as a medium sized koi. The dirt I walk up to at the end of the video is the bogs location in progress haha.

 

[addy1]

I have used bogs for years, so far they have kept my ponds water tests perfect. Little to no algae, never have green water, not even during spring start up, something is working lol. So I think imho, the bio part of my bog works as well as mechanical, but I could be wrong, it works I am happy. If the bio failed I would think the water tests would be off, algae would go crazy. At this point I am happy with my bog, been happy with my past bogs, the last one worked for 10 years, this one has been running for 3 summers, two with a fish load.

 

[taherrmann4]

I put a bog in back in may and made it similar to how Addy has. The only thing I would do differently is that I would have made it bigger, not deeper but more surface area. The only reason being is that I am out of room for all my plants... I had the idea of putting in an 8"-12" pipe all the way to the bottom with small holes throughout the entire pipe. The idea was that I could then put in a sump pump and use it to clean out the dirty water even use a hose and wash the gravel from the top and in theory the dirty water would flow down to the bottom where it could be pumped out. Not sure if it would work the way I think, but part of ponding is experimenting too and see what works and what doesn't.

 

[addy1]

Mine is around 135 sq feet, surface area, and still could use more plant room

 

[Waterbug]

3. Interesting... so it basically only acts like an "all in one" filter for a little while then it loses it's bio filter capabilities rapidly. But it can remain a mechanical filter for years without cleaning is what I am understanding.

That's my take. But the devil is always in the details. For example if you have a lot of pipes under the gravel to direct flow, like some people do, all that pipe will continue to act as very good bio filters because they will, or should, remain clear of muck. If you just pipe water into the top of the bog the area around that high flow will remain clear of muck and provide good bio filtering. If you build a mound of gravel and flow the water over that even more will remain clear and good bio filtering. That's almost a Trickle Tower. If you go a bit further and actually build a Trickle Tower on top of the bog you will have great long term bio filter. Bakki Shower on top of the bog, even better.

The question should never be "is this a good bio filter", the question should be "is this a good enough bio filter for my pond".

What if I filled part of it up with matala mats? Would those help at all with bio filtering? I have a bunch left over from my 55 gallon drum filter. Not sure how I would implement them though.

If you clean the mats as needed they work great. Never heard of anyone actually doing that much work long term, but in theory it's great. Clean media = bio filter. Dirty media = mechanical filter.

5. Okay perfect, I need as strong a flow as possible.

For the fish load yes. The bog is fine with whatever. The beautiful thing about bog, and it really is cool, is that for people who don't want to compute stuff, have high fish loads, spend a lot, want simple, never want to clean a filter, a bog is a great filter for them. Way better than buying one of those big box store filters imo. With a bog you set it and forget it. But there are limits, and fish load is one of those.

I took a video so you can see the fish load. This is about every fish in my pond except maybe one or two, they are all pretty good about coming for feeding time. I also have four turtles, not sure how much they add to the load but I bet it's at least as much as a medium sized koi.

Nice fish. Look very healthy and well fed. That's a pretty large fish load imo and given the current sizes, probably soon to be a huge fish load. I think you need to consider getting more serious if you want to keep those fish long term.

Water quality issues can slowly take fish, or can take them all tomorrow. Higher the fish load the more likely a complete die off. All this filtering stuff isn't digital, these are living animals (bacteria) that live and die. So there no such thing as X number of fish = X gals of bio filtering. We generally way over build the filters as protection from the low points. And we could be next door neighbors, with the same ponds and if we're both running close to the edge I could see a complete die off one day while your water is clear, fish are active and eating. That doesn't mean you have no worries. Your pond just didn't go over the tripping point...this time. It takes serious test equipment to know how close to the tipping point a pond is. Most people over build the filters and pumps so they shouldn't ever be near the tipping point which allows them to not have to buy the test equipment and always be monitoring.

IMO that green water is currently saving your butt. Thank it every time you go out there.

If I might suggest...keep the bog if you want plants, but add at least one or more Trickle Towers on top of the gravel. Super easy to make, almost never have to be cleaned, can be made to look good, even great with a little creativity. They're also set it and forget it but continue to work as a bio filter 24/7. And a much better chance of macro algae growing on the outside which can clear green water imo.

Even better, just the TT and maybe 2" of gravel. Plants can be kept separate from the pond in their own bog if you like. Or make a veggie filter for the plants, even better.

 

[addy1]

I picked up a nice ec meter for some growing I am trying to do this winter. Out of pure curiosity I checked the ec reading of our tap (well), our pond and the fish tank.

The tap and pond did not register on the EC meter, it reads down to 0.2. The fish tank gave me a reading of 0.4. With the TDS meter, our well reading is 47, pond 52, fish tank 200...............humm does that mean the pond is "clean" enough to drink? Or does that mean we should quit drinking our water.........lol Or does that mean the pond is too clean............. per what I am reading the low EC reading relates to low TDS in the pond

I am in the learning curve of hydroponics, at the bottom........... something to entertain my brain if we get snow this year.......

 

[capewind]

OMG Addy... the bottom of the learning curve? Glad I wasnt drinking as I read that or it would be all over my laptop. If you are at the bottom, I havent even made it out of the basement. Thank God hubby understands all this stuff, as I really have no clue.

I added a pic of our bog at the start of construction this spring. The project has been put on hold as we moved all the comets and shubunkins to it for this year.... It measures roughly 8' x 18' x 2.5 - 3' deep ... connect pond is about 6500 gallons.

The filter on the bog is a temp. It has 4 outlets on the front. Two of them, are feeding down to a 2" pvc piping grid he has buried in the gravel so far. The water to the filter is coming from the main pond, and is returned to the main pond via a water fall on the bog... Pump is pushing 8000 gph but is split between the filter box (rated as 5000 gph), and a small waterfall at the other end of the main pond.

I dont know how much or little it works as it is, but the pond is 6500 gallons, guessing the bog is presently holding about 2000++ gallons of water, had a lot of plants this summer, a fair amount of fish (near the limits if based on surface area, but if based on water volume, a light fish load), and ammonia, nitrites, and nitrates all stay at zero.

 

[addy1]

I know very little about hydroponics. I have grown tomatoes all winter in our sun room, this winter set up a room in the basement with lights, fans, it has a laundry tub. Going to try hydroponic growing. We get fresh tomatoes around january, by starting them now.

I love my bog, it takes great care of the pond. Love never having algae issues. I have around 200 fish, counting snaps in the winter when they are calm and just floating. My older ones are around 8-10 inches, They are longer than the spread of my fingers which is 8 inches. When I am in the pond they are all around my legs, best time to check them out.

I saw a few fry, mainly in the smaller ponds. I am sure there are some in the big pond, lots of room to hide.

That is a nice size bog / veggie filter / gf shubunkin pond

 

[capewind]

I really wish I knew just how much bogs can do... I mean support how much. I would say with the plants being moved or dying back, and doesnt the bacteria die once the water hits a certain temp? maybe see what the nitritate/nitrate levels do then??

For the last 3 days, hubby has gone out for 5-10 minutes to take a quick look for fry... 21 so far! I think 2/3rds of them are comets, and the rest shubunkins... but I am surprised at how small some of them are. Each day we are getting some really tiny ones (2-3 each day)... I mean just a couple or few days since their little suction cup thingys release... still transparent, and their bellies are not streamline yet, but big bubble thingys LOL. Sorry for my poor vocabulary LOL. I know it is a normal stage as I was staring at the ones that were spawned inside constantly, I just dont know what things are called LOL. I'm going to guess we still have 700-800 water hyacinths in the main pond, plus all the creeping primrose roots,,, God only knows how many are out there!

 

[Waterbug]

I really wish I knew just how much bogs can do... I mean support how much. I would say with the plants being moved or dying back, and doesnt the bacteria die once the water hits a certain temp? maybe see what the nitritate/nitrate levels do then??

You can test what your bog, each is different. Place a pump in the bog where it normally overflows and pump water back to where water normally enters. Add ammonia to the bog water until you get to 0.1 ppm. Each day measure ammonia and nitrite and try and keep ammonia at 0.1 ppm but track the changes. After you see nitrite rise and then fall, or never rise at all because that bacteria is already there, you know you have a bacteria colony.

Now you can then simulate fish load by adding ammonia for the amount of fish load you want to test and can track how the filter handles the load.

Never heard of anyone doing that with a bog before, but that's how filters are tested to find out conversion rate. Water temp, pH and KH are also factors. Normally this testing is only done on what high fish load keepers would consider to be bio filters.

As temps drop so does the conversion rates of nitrifying bacteria. Converts like 25% of normal at 45-50F, 0% at 39F.

 

[capewind]

I am so blonde tonight... most of your instructions went right over my head LOL. Intake for the bog is in the main pond, runs through a filter, then into the bog, to a water fall, back into the main pond....

 

[Waterbug]

Sorry. I'm sure it will be fine however you do it. That's one of the bennies to this type of filter, you really can't get it wrong....rocks and water is all you really need, plants if you like. Nature does the rest. This, that and the other thing are just little tweaks and probably unimportant.