Planning a bog filter / water garden

[csdude55]

I've done some preliminary research, and now I have questions!

I'm attaching a few pics of my pond; they're a few years old so you don't see the plants I've done, but you can see that in the first pic I have a bit of clear space on the right of the pond that's part sun. The pond itself is just under 1,000 gallons.

So I'm thinking that I can build a 150-200 gallon bog in that clear area that's part sun. I'm thinking around 3-4' diameter and 2-3' deep, give or take.

If I understand correctly, I would leave the submerged pump in my pond, and pipe it to the bottom of the bog (capping the end of the pipe and drilling 1/4" holes throughout the pipe where it lays at the bottom of the bog). Then layer the bottom of the bog with pea gravel until it covers the pipe by a few inches, then backfill it with the dirt that I dug out.

So far so good? I feel like there should be a layer of something between the pea gravel and top soil, but I don't know what.

First question: how do I pump it back from the bog back to the top of the waterfall, so that the filtered water flows back in to the pond? A second pump seems like a mistake; if one is pumping harder than the other then I'm either going to run dry and burn one up, or overflow the bog.

Second question: I'm hoping to put some plants in the new bog... my new pitcher plant, maybe some of my excess pickerel rush and creeping jenny. Maybe a bromeliad? I'm not sure. Which means that I'll need to put some stepping stones in the middle so that I can get to the plants. Do I just plant them in the soil and trust that the water is going to stay at the right level? What's the "usual" plan for that?

 

[Tula]

I'm in my first season with our small bog so not too experienced. We have a separate pump for the bog and only have pea gravel in the bog, no soil

 

[Mmathis]

Most bogs I am familiar with are solid pea gravel — the topsoil doesn’t go back into the bog.

 

[poconojoe]

No soil in the bog. The standard is 12 inches of pea gravel covering your manifold pipes, that's it, nothing else on top of that. Smooth gravel or river rock is preferred because you don't want anything sharp that can puncture your liner.

A lot of us cut slots 1/3 through the PVC instead of drilling holes. I made my slots 1-1/2" apart. Slots, to me, are less likely to get blocked by the gravel. They are longer. A hole is just one spot.

Manifold pvc pipes should be at least 1-1/2 " diameter, 2" is even better. If your pump has a smaller diameter output, run the hose over to the bog and use an adapter to increase the size. The idea is that a larger pipe will have a less tendency to clog.

The water gets pumped from the opposite side of the pond. It travels through the manifold pipe(s) and works it's way up through the gravel and flows back to the pond.

The walls of your bog need to be higher than the bog's water level. You create a low spot or notch in the wall between the bog and the pond for a path to guide the water back to the pond. This can be a waterfall, small, large, high, low, it's up to you. Height of the waterfall is determined by the water level of the bog.

As you can see from the last picture, I made my bog walls a bit too high. I was maybe just a little paranoid!

 

[poconojoe]

You're gonna love the bog. My water has never been so clear.
The bog size is not determined by gallons per se, it's usually sized at 30% of the surface area of your pond. Measure the approximate square footage of your pond's surface (length x width). 30% of that will give you the square footage of the bog surface.

 

[poconojoe]

I have a clean-out stack on the ends of my manifold pipes. Each one has a threaded cap on it and they stick out above the gravel a bit for access. It's just an extra precaution in case I want to flush them out.

 

[poconojoe]

The gravel acts as mechanical filtration and a place for beneficial bacteria to colonize. The plants thrive on the excess nutrients in the water. The result is clear water returning to your pond.
Mine cleared up in 6 days after turning it on. And at that point the plants had not even gotten established yet. All the plants I put in the bog are thriving.
Oh, and yes, you can lay a few flat rocks in there to step on. Or just step right on the gravel.

 

[csdude55]

Ohh, I see. I was blending some information with what I'd read here for a bog garden:

How to make a bog garden for wildlife

Have fun with exciting, flamboyant plants and create a stepping-stone habitat between wet and dry with a back-garden bog garden.

www.discoverwildlife.com

Having to build the bog to be higher than the pond is a bit of an obstacle, though... you can see that I have a fence that's about 3' behind the pond, and the border is raised to make it level and to prevent rain runoff. I own the land behind the fence, too, but it slopes downward and away from the pond. So I don't really have an area that I can build up to be higher than the waterfall... I guess I could make like a cinderblock wall that's 3' high, then surround it with dirt and river rock to look sorta natural? But I'm afraid that it would just look like a great big pile of rocks.

I'm gonna have to think about this one. I hate to say it, but my front yard slopes downward, away from the house... everything keeps pointing towards me doing a full waterscape in the front! I could do a bog at the top that falls to a 500g pond that falls to a 2000-3000g pond. I'll have to get some heavy equipment to remove some oak trees (that I honestly don't like, anyway) and level all of the ground out, but after that everything else would be easy.

 

[poconojoe]

Your existing waterfall is quite high. You can build the bog along the fence and above or partially below grade. Then just have a low spillway back to the pond. If you really want to keep a tall waterfall, rebuild it in another area of the pond.
My old waterfall was tall, but that height was not feasible when constructing the bog.
The bog walls can be built with many different materials. I used rocks which were plentiful on my property. My bog is partially below grade. You can build the walls with timbers, 4x4's, concrete blocks, etc.

 

[mrsclem]

Your article you posted looks like its for a bog garden, not bog filter. Basically a garden that stays very wet. I have one behind my ponds where my filters get flushed to. Bog filter is gravel and needs to have a way to gravity flow back to the pond. Mine are built from 2x12 lumber and other one is 150 gallon stock tank.

 

[addy1]

Then layer the bottom of the bog with pea gravel until it covers the pipe by a few inches, then backfill it with the dirt that I dug out.

I would not use topsoil the constant water flow will be sending that dirt right into the pond. I used just pea gravel.
That is a good way to make a bog garden, not connected to the pond.

 

[csdude55]

@poconojoe, yeah, my waterfall is about 3' tall, but I really like the sound of it splashing I have a shady reading area about 15' to the side, and a hot tub built in to the deck that's also about 15' away, so I love kicking back at twilight and hearing it in the background <3

Buuuuut, maybe it's time to change things up a little.

I'm doing some planning on removing the boulders and waterfall, then use cinderblocks to build the bog "container" and surround it with river rock. None of that's really on my land, though, all I have in abundance are field pines and red clay soil! LOL So I'm looking at about $500 in materials. I'm planning to build the bog about 1' higher than the pond and slightly overlapping, so that the runoff makes that nice splashing sound.

I honestly was thinking of the substrate like a homemade water filter, though, where you would use pea gravel as the macrofilter, then activated charcoal to kill bacteria, then sand as a microfilter. So just using pea gravel blows my mind, I can't grasp how it filters so well. Good bacteria, sure, but my foam filters have the same bacteria (it has a macro, then some plastic balls for bacteria, then the micro) and it barely seems to do any good at all. I'm still gonna try it, I just don't really understand the logic.

 

[mrsclem]

It's not the gravel that works to filter in a bog but the plants. They pull excess nutrients from the water.

 

[poconojoe]

Sand will clog. You only want pea gravel. No sand, no soil, just pea gravel.

Another note: All my plumbing is within the pond and bog. If there's ever a leak in the plumbing it will only go back into the pond. A leak in any of the plumbing can never drain my pond.

Check out this very informative site:

Build an Active Gravel Bog Filter - Nelson Water Gardens and Nursery

Nelson Water Gardens & Nursery is your Katy, TX nursery. Come visit us to see our wide selection of plants, fish, and water gardens.

nelsonwatergardens.com

 

[csdude55]

Thanks for the link, @poconojoe, that's very informative

I guess where I get hung up, @mrsclem... I have plants already in my pond (parrot feather that I thinned out a LOT today, 2 pots of pickerel rush, and 3 pots of pond lilies), so if it's the plants that do the cleaning, why aren't they helping without the bog? What more does the pea gravel bring to the table?

And I mean that as a sincere question, not being argumentative. My girlfriend's gonna kill me if I spend all Summer and a bunch of money building a bog that doesn't make any difference! LOL

While we're talking about bog plants, if they're what's doing most of the work then what happens over the winter when they've died down?