Adding a bog filter to my 600gal pond


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After many problems with pond liner leaks and failed patches, I opted to drain and refit a new liner. I though this was a perfect time to think about an upgrade and to add a bog. I went for a bog that is the same size surface area as the pond, although only 12" deep, compared to 3ft in the pond.

This is my original pond:
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Then this is what it is like today after the relining and the new bog added:
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Next stage is to create the bog filter piping. I am getting some flex pvc tube to attach to the pump, which will supply water to the bog into 40mm rigid pvc piping with slots cut in. The 40mm pvc pipe will have a capped vertical terminal for cleaning. Then I can fill with shingle and think about plants.

Finally I am also thinking about what border I'm going to have for the bog. My first thought is to cut back a bit more turf and have a pebble/rock border, but not yet decided. Whatever it is I want it to be wildlife friendly.

So it's not gonna happen overnight but I'll get there soon hopefully.
 
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Great job! Of course with more filtration you can have more fish :)

For symmetry I might copy the pond border.

Or, If you make a shelf just under your bog liner you can use different rocks on the shelf and just above it to hide the liner. And you can plant at the edge of the bog both in and out of it, so the edge is more hidden.
 
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So I got all the kit, 3m of 25mm flex pvc pipe, and a few metres of 40mm rigid pipe with various curves and a reducer. I chose to solvent-weld the manifold rather than push fit.
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Next I cut the slits at 6" spacings. For this I used my mitre saw as I can easily set the max cut depth and then it's quick to do the whole run.
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The bottom of my bog is curved, so i used a heatgun to heat the pipe and put a slight curve in it so it followed the base of the bog. Next I plumbed it in and filled with stones. I'm a bit gutted as my water was crystal clear before this stage but despite rinsing the stones many times, some of the limestone chippings I used turned the water cloudy and hasn't settled yet! Might have to replace entire pond water. I emptied a few inches and will see in the morning. Of course from the pics I haven't finished the design yet so that is still to come. The bog has been created to feed level with the pond but now I quite like the waterfall effect that happened with the pond water a bit lower.
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Nice! As per the knowledgeable folks on this forum, I would take the plants out of the pots, but you probably already thought of that. I’m sure your water will clear up soon.
 
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Nice! As per the knowledgeable folks on this forum, I would take the plants out of the pots, but you probably already thought of that. I’m sure your water will clear up soon.
Yes they're just there in pots temporarily until I decide where to finally place them, and also until I learn whether any of them need to remain in pots for spread-containment reasons.
 
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Ok ive learnt my first lesson today on siphoning. My pond pump went off (its on a timer) at 6pm as usual, and later I went to look and all/most the water siphoned out of the bog. So I looked up on here and read a few threads about needing a hole to stop the siphon. I am not sure yet how I can do this, but it might mean I have to cut into the flex pvc and have a vertical snorkel up out the bog at the entry to the bog.

I haven't yet worked out whether I should or shouldn't continue with the timer, as that was there to stop the fountain going all night.
 
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Ok ive learnt my first lesson today on siphoning. My pond pump went off (its on a timer) at 6pm as usual, and later I went to look and all/most the water siphoned out of the bog. So I looked up on here and read a few threads about needing a hole to stop the siphon. I am not sure yet how I can do this, but it might mean I have to cut into the flex pvc and have a vertical snorkel up out the bog at the entry to the bog.

I haven't yet worked out whether I should or shouldn't continue with the timer, as that was there to stop the fountain going all night.
Hi. Very nice job and of course the cloudy water will clear up in a few days so no need to change it. One question. I never heard of turning a pond pump off. All mine run 24/7. Is there a specific reason you want it off?
 
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No change in the cloudiness overnight ☹️. The pond is currently only 2/3 full, so I have to decide whether to add the 1/3 and hope that the cloudiness subsides over time, or sod it and empty the whole thing and start again. The water is only 4 days old as it was fresh from the tap when the new liner went in, so no concern about losing good stable bio water.

As for the pump, I have one of those all-in-one pump filter fountain things. I've always had it on a timer so that the fountain doesn't run all night. I guess I turned it off as I thought that I don't see the fountain over night so save some energy. As it now serves as the bog source then perhaps this is no longer the right decision.
 
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Ok ive learnt my first lesson today on siphoning. My pond pump went off (its on a timer) at 6pm as usual, and later I went to look and all/most the water siphoned out of the bog. So I looked up on here and read a few threads about needing a hole to stop the siphon. I am not sure yet how I can do this, but it might mean I have to cut into the flex pvc and have a vertical snorkel up out the bog at the entry to the bog.

I haven't yet worked out whether I should or shouldn't continue with the timer, as that was there to stop the fountain going all night.
Probably a good idea to keep your pump running 24/7. For one thing, they're built for this, and starting and stopping can (supposedly) shorten the life of your pump. But more importantly, you want a constant flow of oxygen running through your bog to support the nitrifying bacteria. While reducing the flow when temperatures go down can save on energy, you don't want to stop it altogether.

As for an anti-siphon device, you can either install a check valve, or simply create a way for air to fill the pipe if the power goes off. Ozponds has a nice video on how to set this up:
 

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