Thoughts on a *small* bog area

[Shdwdrgn]

I've been rebuilding my waterfall area the last couple weeks due to the liner sinking, leaking water over the back edge, and the wood rotting out. So now I have a nice wall made of redwood 2x6s and I've been using the pond tape to seal and extents the liner up over the higher wall.

In the meantime, I've been playing with ideas for the waterfall basin. Basically I have two 55-gal filter barrels sitting apart, with a basin area in between them, and a stone wall built up in front that creates the spillway for the waterfall. I have wanted to use this basin area as a small bog filter, but my first attempt failed.

For my new setup, I have T-ed off the 2" pipe going into each barrel so that about 2/3 of the water flow now goes into the basin area. That pipe also has a T on the end, so I ended up with two connected pipes spanning across the bottom of the basin area. However, there are not actually 'pipes' spanning across, rather I took some 1/4" screen and rolled it into a tube to form a hollow area. The idea is that I pour rock on top, and the screen will ensure that a hollow area is left behind, through which the water and waste can flow up into the gravel bed. With me so far?

All right, so the idea is to put down a thick layer of 1" river rock over the pipes, then finish it with a thinner layer of pea gravel to set the plants in. The entire basin area is small by bog standards, maybe 14" x 24"? Since it's available, I might as well use it, even if I don't get a huge amount of filtration. I'm hoping it will act more as a polisher since the rest of my setup keeps the water fairly clean anyway.

So my question in all of this... Does the layer of larger rock topped by pea gravel sound correct for providing a good area for waste to break down in? Should I include anything else when I put down the rock layers?

And one more thought -- will the waste breaking down in this area create a more acidic layer, like a peat bog? The reason I ask is that I would love to get some carnivorous plants growing, which love the conditions of peat bogs. It would be nice if this area worked out for that purpose.

 

[Meyer Jordan]

Refresh the Forum's collective memory. Is your pond still 1600 gallons?
If so a 'bog' this small will not have any appreciable effect on water quality....good or bad. Even if you made it 18" deep, after deducting the space taken by the rock and gravel you may be lucky enough to have space for maybe 10 gallons of water. A 'bog' this small will also have problems with excessive flow rate since you are going to tie it into the waterfall.
In answer to your last question about acidity, this would also be prevented by the flow rate.
Incidentally peat bogs (true bogs) do not have any moving water. The source water is entirely ground water usually replenished only by rainfall.

 

[Shdwdrgn]

Yes, about 1500-1600. And there is probably 10-12 inches ofwater over the top of the pipes.

Hmmm. Well that's disappointing. Since everything is already in place I'll be setting it up anyway, at the very least if should help plants grow well in that area.

 

[addy1]

Even if it does not help a lot it can look great with some plants growing there. To me the more plants you have eating up nutrients the happier your water can be.
You could try carnivorous plants, I had one in my bog/gravel filter, the poor thing got lost in the other plant growth. They prefer wet dry sequence. But try one it might do fine. Put the plant in a mound of pea gravel so the crown is above the water.

 

[ChrisP]

Any plants help with filtration.

It sounds like the "full force" of the water will go through this area, but with a little tunnel for most of the water to travel unimpeded. Therefore, the pH level here will be the same as in the pond - no acid loving plants.

I have a couple of spots in my waterfall where I've created a dam and filled in with pea gravel - the water runs through and over it. I have various tropical plants and water mint there that do just fine even with 3000 gph across those sections.

 

[Shdwdrgn]

Well, all of the water from the pumps goes over the *surface* of this area, but I have plenty of pea gravel and was planning on raising some of the bed up above the height of the water. Basically the water volume is split, so half of it goes into the barrel filters (then spills out into this basin area), the other half is pushed through the undergravel pipes to provide water flow up from the bottom of the rock bed. Because of the back-pressure from trying to push water under the gravel, I expect only about 1/3 of the water will actually flow underneath the gravel once it is in place though. Also I am running two pumps at 2900GPH *each*, so quite a fair amount of water flowing through the system... But yeah, as you say, with the continual turnover at that rate there is not way the pH would change within the bog area.

 

[Shdwdrgn]

I finally finished rebuilding the waterfall basin area yesterday and got some pics today. so far I've very happy with what I'm seeing! I started off making sure there were no leaks showing up behind the liner, then picked up some 1.5" river rock the landscaping place had available. A quick rinse got most of the clay off of them, then they got dumped into the waterfall basin. I also pulled on the liner after there was some weight on it, can't hurt to give a little extra space to prevent leaks around the liner folds. Anyway I filled the area with the river rock to about 4" under the water level, then added 2-3 inches of pea gravel on top.

The row of large rocks at the front edge have always helped prevent most of the pea gravel from washing over the falls, and the provide just enough turbulence to really even out the flow of water coming from the barrels, so I end up with nice sheets of water spilling over the edge. The grasses came from my stream so I know they'll be fine in the flowing water, and they stay less than a foot in height.

The best part of all is the pipes running underneath the gravel. Previously the entire back half of the basin area was a dead stagnant zone. Now there is water flow coming up through the gravel, even at the very back against the liner. It's not much flow, but if you stir the pea gravel with your finger, you can easily see sediment flowing forward towards the falls. There is one undergravel pipe near the back, and a second one just forward of the half-way point.

Of course the new rock layer add back-pressure to water trying to run into the new pipes, so I have a little more water flowing into the barrels than I expected, however I'm not too worried about that. As everyone said, a low water flow through a bog is a good thing, and I can always make adjustments to the plumbing on the top side to adjust the flow as needed.

Do you think they approve? The water has been running pretty clear this year since I got my algae problem under control, but it still has a bit of coloration to it. I want to shut off the pumps and take a closer look again next weekend to see if the new bog area is actually trapping any of the suspended sediments. It's always had a bit of a tea color to it, but it would be nice to see it clean up crystal-clear. I'm excited to have another type of filtration on the pond now. This is what I originally intended for that basin area, it's just that my first attempt didn't work (at all). Now I have water flow, so something positive has to come from it...

 

[addy1]

looks really nice

 

[pecan]

I absolutely love it! Great idea for the extra space. Next year, those plants will be filled in with that cool rock wall in front and water flowing out from under the green plants and over the wall. Very cool. I think you will really like it. And while there may not be a lot of filter benefit (but I think any plants add filtration though, just might not be a ton), its great to look at.

 

[addy1]

Every tiny plant helps some, even if only a tiny bit.