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| My pond is about 5' x 10', sort of kidney-shaped, with an average depth of 3'. By the time I wrestled with what to do for a stream (almost 2 years now!), I ended up with one 20' long. The pond seems small now, by comparison, so I've toyed with using the uncut excess liner to make a bog / plant filter extension on one end. I'd like opinions on what anyone sees as pros or cons to my plan.
Another consideration in this, is that in the original excavation, I marked the perimeter with a 1 foot "shelf", just a couple of inches below grass level. I don't want the "rock necklace" look, however, so I flooded and inch of water onto this shelf, making the pond look a lot bigger, then toyed with ideas of how to finish it. In the meantime, it has provided a great ledge for frogs to hide on, underneath the rolled up liner. Anyway, this is my plan:
You can see the original perimeter shelf at the top. I dug the bog to the right of that. With the original shelf in place though, this leaves a liner eyesore, just under the water. My plan is to cut about 5" off the height of this shelf, leaving it about 6" under water. Then I'll fill the bog with pea gravel, sloping from water level at the right, and meeting up with the new shelf level, 6" under water, at the left. I figure that this will give me lots of flexibility with planting depths for marginals - from 0 to 6". This will also give frogs a convenient ramp to get out of the water, regardless of fluctuations in the pond's water level. Supply water will slowly percolate up through the pea gravel, over the underwater shelf, and into the pond. I thought that using some kind of fine particle substance in the bog (special soil?) might form a better filter, but I seem to be seeing a concensus that it's best not to introduce anything with nutrients, but rather, force the bareroot plant anchored in the gravel, to pull nutrients from the water, to keep algae in check by competing for its food. That's about it; I look forward to anyone's feedback. Thanks, David |
Follow-Up Postings:
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- Posted by sleeplessinftwayne z4-5 IND (My Page) on Wed, May 21, 08 at 12:38
| Hey, David. I am trying to get a good idea on bogs myself so I suppose I am going to ask questions rather than give you the benefit of my extensive experience. (I wish!)I understand the way you have it set up and I have had the same arrangement with a 2' deep pit and the input going to the bottom then perking up through the pea gravel. Is that how you are doing it? I ran it for a year that way and ran into a problem or else didn't recognise what I had. Over that year, with the water perking up through the gravel, even with a fair amount of pre-filtration there was a substantial deposit of particles throughout the gravel. The deposits became very tight with the incoming water forcing it's way through channels that were very difficult to eliminate. Incoming water eventually left the gravel just as dirty as it went in. I was able to divert the channels somewhat by cleaning some of the gravel down to the bottom but that seems to negate any benefit and was time consuming, dirty and backbreaking. Did I do something wrong or did I just stop the process too early? The root systems of most of the plants was dense and weeds had to be removed fast or they became monsters. Roots of Sundrops for example were almost a solid mass. Did I need a larger volume of gravel? Could I have made it more shallow, wider? I would like to hear more of the details of your bog. Good ones seem to be rare. Sandy |
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| Sandy, Given that you've actually made and operated this type of design, and you're the only one that's responded so far, at this point, you're the expert here! I'm gathering that a bog is more like a damp soil/peat garden than the flooded hydroponic pebble bed I'm doing, so maybe plant filter is a more appropriate name for this. My plan would indeed have water percolating up through the pea gravel. I know I've seen recommendations of having bottom drains, so sediment can be flushed out, but this would require that the plant filter be a raised unit with a hole through the liner, which mine won't be. Maybe this approach with constant flushes would avoid your clogging, but this seems way too high maintenance for my liking. I suppose if you did just let the process go, you'd get a consistent "clog", but I wouldn't think this would form a contiguous filter; it would more likely just plug the overall flow. I've also seen recommendations of a grate above the supply pipes, to keep a clear water channel along the bottom, but I'm not sure that would change the clogging issue you're experiencing. What are the details of your supply piping? Your experience with clogging and water exiting just as dirty, jives exactly with my musing that "using some kind of fine particle substance in the bog (special soil?) might form a better filter". I suppose that with no fine screen to catch the fine particles, the pea gravel media may allow plants to extract nutrients, but won't help much with water clarification. But then any complete fine screen layer would just catch all these particles and clog - I don't know how you win this game. I don't really have any more details than were in the original posting. Hopefully, someone else with experience in this can help us both out! David |
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| Sandy, Got an idea from the guy who got me into this mess in the first place. You see, my wife came home with a Canadian Tire (read "Walmart") pond kit, and I had to open my big mouth and say, "If you want to do a pond, let's do a pond!". The other thing you need to understand, is that I'm a bit of a perfectioninst, so I'm determined to get all the key factors right the first time. (Hence I'm two years in and still don't have the stream flowing yet!) To give you a little background, we know this guy who's dad runs an aquarium supply business, and he's done a few ponds on the side. His advice has always been great - steep sides and no shelves that are too shalllow, to keep our raccoons, herons, etc. - come to think of it, my plant filter plan violates this wisdom somewhat; we'll see what happens. Anyway, he said when he did something similar to my plan, he simply did a side-flow of water, not bottom up. I'm thinking this might work great. Run a supply line all the way around the outside - on the right-hand side of my diagram, about level with the new shelf height, 6" below water level. Now, you get primary flow sideways, and anything that settles gets pushed by the flow, into the bottom half, forming a kind of soil. At least that way, early "clogging" of the bottom won't block flow, and I can monitor and reassess after the first year, if changes are needed. (I'm hoping it will simply become a boggish soil, and I won't ever have to dig this out to clean it!) Maybe your timely warning about clogging, and his apparent success with side-flow have pointed me to a promising solution. David |
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- Posted by magdaloonie 6 - high desert (My Page) on Sun, May 25, 08 at 20:51
| Boy, sure could use an EXPERT here! Instead, I'll chime in. I haven't built one yet but I've been planning one and there's an element I'm intending that neither of you have mentioned I'm planning a rigid mesh barrier in the bottom that'll leave about a 3-4 inch space in the bottom (where the plumbing is) and then a 4" pvc pipe will go all the way through from just above the surface to the very bottom. "U" cut outs in the bottom. The purpose being to give the muck a space to settle in and then be able to vacuum it out through the pvc pipe. I thought I could also flush through the pvc, too. I'm not saying this'll work but somewhere someone did something like that and it stuck in my head. Hows that for an endorsement? Vanessa |
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| Vanessa, Actually, I did mention the barrier in my first response to Sandy: "I've also seen recommendations of a grate above the supply pipes, to keep a clear water channel along the bottom, but I'm not sure that would change the clogging issue you're experiencing." If indeed the muck only settled in the very bottom, then your approach may work, provided that when you get to the bottom through your 4" pipe, you can still access the entire bottom area. In Sandy's case though, it seemed like she was getting clogging throughout the entire depth. How do you plan to diguise this 4" vertical pipe? |
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- Posted by auminer49r zone 5 (My Page) on Wed, May 28, 08 at 12:07
| I am struggling with the same questions as I plan out a similar bog filter for the 10x10x3 pond I just dug. I have not done this before but I have spent hours researching over the last couple of weeks. Maybe we can put our heads together and learn from each other. Some things that I have read recently suggest having about 50% of the surface covered with lillies and 1 bunch of anacharis for each sq ft of surface area. Also, koi will eat your lillies so goldfish are recommended instead. Too many fish will cause more waste than the plants can filter. Be conservative until the pond gets balanced. It is also recommended that the fish are not to be fed at all. They can eat the anacharis. Like another poster mentioned; an open area at the bottom of the bog may collect sediment. I wonder if too much pump flow forces the sediment up and through the filter. Maybe the flow needs to be reduced or maybe landscape fabric over an egg crate (from flourescent light covers) could cause the sediment to drop out in the bottom of the bog to be cleaned out. I have never heard of anyone using landscape fabric in a bog, but it makes sense to me, if it is safe for the fish. |
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- Posted by magdaloonie 6 - high desert (My Page) on Wed, May 28, 08 at 16:00
| Dang. It's getting so complicated. But I think some of the issue is whether your bog filter is your sole/primary filter or not. Mine is intended to be a place to grow more plants and justifying the expense by saying "yeah, but it's a FILTER!" My skippy is actually adequate for the size of my pond and my fish load so this is more decorative. Sorry I missed the mention of the grate in your first post, David. Guess I read too fast. I figured to paint the portion (just a couple inches) that's above the waterline dark green. Then the plants better grow as that's the whole point. |
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- Posted by prairie_bogger 6a (KS) (My Page) on Wed, May 28, 08 at 21:13
| I'm pretty sure I've posted this link here before, but hopefully it can help in some way. We've had our bog filter for almost 3 years, which is too early to say whether it will continue to work well or not, but I do like the fact that I don't have to water or fertilize my plants ever :-) The water has remained clear and we haven't noticed any clogging yet. We've flushed the clean-out pipe once. |
Here is a link that might be useful: Bog Filter
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- Posted by sleeplessinftwayne z4-5 IND (My Page) on Thu, May 29, 08 at 5:31
| Thanks for the link. It gives me ideas and hope for much less cleaning. Vanessa, I did the whole thing again with 1-2 in river bed stones and got the same results. I spoke to some old friends this week and they tell me the channels are a natural development when you have a deep rubble or stone bed and is the best thing that can happen. It was just too small a container for the depth. Looking at the link, I suspect if I can go that large I would do myself a favor to dig a trench with perforated PVC to collect anything that sinks and then I can collect it once every year or so. Sandy |
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- Posted by auminer49r CO, 5 (My Page) on Thu, May 29, 08 at 10:35
| that's a beautiful pond, prairie bogger. I like the way you hid your cleanout pipe. I am so encouraged to read about a successful pond with a natural looking filter. I would love to hear more about your philosophies on plants, fish, bog size, flow rates, etc... My hat's off to you. , Jason. |
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- Posted by sleeplessinftwayne z4-5 IND (My Page) on Fri, May 30, 08 at 4:24
| Ditto, Jason. Maybe one of these days I will stop experimenting and settle for beauty and efficiency, too. Vanessa, I forgot to mention, I had a few handfuls of lava rock in there and it made life miserable. I have learned to hate the stuff. My hands get roughed up enough with out many cuts and scrapes that get infected as well. Sandy |
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- Posted by prairie_bogger 6a (KS) (My Page) on Fri, May 30, 08 at 18:06
| Thanks Jason and Sandy :-) Ouch Sandy! I have limited experiece with lava rock, but I can imagine the discomfort. I think experimenting is great fun-- you never know: one day you might be the one to discover the perfect pond setup that nobody else thought of! Sorry I don't have much of a philosophy on ponds, Jason. I too just keep experimenting and hoping all goes well. Of course, reading the wealth of knowledge on this forum doesn't hurt either. :-) What you can't see in the photos is that our pump won't prime when hooked up to the skimmer,so right now there's a big black intake hose sitting on the pond bottom with a strainer designed for a sump pump attached to the end. Real beautiful. When I complained, my DH's only comment was "Well, there's the bottom drain you always wanted!" I probably should add the statistics of our pond to the bog page, but the size is roughly 15x30' x3.5'deep, the bog is a little less than 1/3 that size and about 2' deep. David or anyone else that migth still be interested-- here is a link that was helpful when we started researching bog/veggie filters. If nothing else, it has a great list of plant to try in and around ponds & bogs. Sherry |
Here is a link that might be useful: Nelson Water Gardens -Bog Filter Construction.pdf
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| Well thanks for the info there folks. I am just in the brain storming stage. Not sure what the design will be but my main goal is to provide habitat for frogs. I read on a site, SC Natural Resources(scdnr.org) I think, that they often wont lay eggs in water if they detect fish. Any of you have any experience with frogs in your setup? I am thinking of collecting rainwater run off along with a valve that taps into a rain barrel to keep the water level topped off. I will try to explain that better if anyone is interested. |
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- Posted by auminer49r zone 5, CO. (My Page) on Wed, Jun 4, 08 at 20:16
| Thanks for the great advice. I was reading Nelson's Bog Filter PDF and I noticed that they recommend planting with a rootball of soil versus bare root. I will be afraid of gunking up my bog filter, but I want my plants to thrive. I may wrap the rootballs in burlap... or keep researching and see what the seasoned veterans are doing. Nelson's design is different than mine in that they recommend practically putting the bog in the pond. I think that Davids design should work fine. I will make slits in my distribution pipe with a skillsaw just on the bottom half of the pipe, instead of drilling holes. It should keep from sucking up pea gravel when I backflow the filter during cleanout. , Jason |
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- Posted by magdaloonie 6 - high desert (My Page) on Wed, Jun 4, 08 at 21:23
| Lots of exciting info here. I feel pretty sure that by the time David and I actually build something, we'll have a good idea of what we're doing...then we'll change it! So be it. I'm now thinking of replacing my skippy with a larger bog filter rather than adding as a second filter. Sherry, I wonder if anyone else thinks 3 years with no problem sounds GREAT! I don't expect this to be no maintenance so your bog sounds - and looks - pretty good. Even if you have to dig everything out next year and wash the media you're still ahead of the game in my view. Jason, I was thinking of using fabric pots with soil for the same reason you're thinking burlap. I want to include some soil without gunking things up but I know burlap breaks down pretty quickly. Those fabric pots are not very expensive. Someone here makes her own with landscape fabric. Sandy, I will take your lava rock warning to heart! I may still use it but I'll wear some heavy gloves or something. I did forget how rough it could be and that my hands will surely be in it! Vanessa |
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- Posted by auminer49r zone 5 (My Page) on Mon, Jun 23, 08 at 14:21
| Well, I did it. I have my bog filter up and running. I am very pleased with my water after 2 weeks in the sun. No algae. My water tests are great. However, I am dealing with dust from pond excavation and pea gravel quarry dust. Even though I washed and washed it, it is very difficult to get the pea gravel clean. Now I have a thin coating of sand on the bottom of my pond, but my water is clear. I appreciate the advice from you all. I have very few regrets about the way I built the pond. , Jason |
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- Posted by prairie_bogger 6a (KS) (My Page) on Tue, Jun 24, 08 at 8:10
| Jason, I remember how hard we tried washing the gravel and how upset I was when we started up the pump and all of this brown water came flowing out of the bog. However, it really doesn't matter and you probably won't even notice the sand in a few weeks. I hope your pond stays clear, but don't be surprised if it does turn green for a while. Our pond was clear for a few weeks after we put in the bog filter and then turned pea-soup green for about 6 weeks before clearing up for good. If it wasn't for all the great advice and assurances of this forum, I'm sure I would have done something drastic instead of having the patience to wait it out. Would love to see photos if you get the chance to post some! Sherry |
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- Posted by montanawanda 4-5 (My Page) on Tue, Jul 14, 09 at 12:11
| I am a newbie to the bog filter concept. I am trying to decide if a bog/veggie filter, aerator or UV unit would be the best choice to help my 40' x 70'3 year old pond. It has turned to pea soup each summer when it turns hot. I have plants, 7500 G. pump and bio falls, a few fish, trapdoor snails. It is in full sun but trees around it are growing. I have read all the responses to the bog filter so far. Any help or advice would be appreciated to prevent this green water algae. Thanks montanawanda. |
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| This is only my second year with a pond but I have a bog where my waterfall is and the pond store where I buy my supplies told me to fill the bod with lava rock. The kind you buy in the bag at lowes. It works really good just make sure you rinse it good first. Hope this helps |
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