400 gallon pond with bog

[IPA]

I'll apologize now, this post may be a little TLDR. I am in the process of building a pond and have a few questions. I am using a 10 x 15 epdm liner and plan to have a depth of 2 feet; about 1 foot in ground and 1 foot above due to flooding. The footprint will be about 5 x 10 but won't be rectangular.

I have a design that I was ready to move forward with, from above it is a bit of a slanted "P" shape for the pond, the part that isn't in the "P" is the bog.

First set of questions is how deep should the gravel in the bog be, including the height of the PVC pipes or not? I have read 12" max (does that include the PVC height?) but also 18" to 24" to prevent the plant roots from clogging the pipes. Also, with the small size of the pond and bog I have read 1.5" PVC is okay, but would 2", 2.25" or 2.5" be recommended

Secondly, what intake filter or debris guard should I be using for the intake on the pump? I like the idea of a skimmer as there is a weeping willow close by as well as the many benefits to a skimmer. On the down side, I have tadpoles from spring to fall and would like my fish to spawn. Having to check the skimmer every day or the thought of loosing fish makes it unappealing. A part time skimmer is something I can engineer or purchase later. My main concern here is protecting the pump by excluding large debris into the system that doesn't require constant cleaning.

That leads me to my next set of questions. Has anyone used a downflow (water drawn from bottom) bog? What is the disadvantage of the downflow design? Also, What kind of work loads do the bogs put on the pumps? I bought a Danner HY-drive 1900 pump (sku 20210) with a sharp fall off: 1' is 1710, 3' is 1325 and 5' drops to 870 gph. Is this too much pump or just right? I also have a 9w UV filter that I've been using in the 50 gallon and will need to use a diverter as I think the UV will be more effective at a slower gph; or am I wrong there? Thanks for reading and any advice that you'd like to offer is appreciated.

 

[Lisak1]

Lots of good questions - I'll let people who are better at construction answer those! I just wanted to say welcome to the GPF! Ponds are fun!

I do have sort of a downflow bog - we have a negative edge pond (acts as a skimmer) that flows into a gravel filled pit. The pump vault is in the pit with the pump at the bottom.

 

[JBtheExplorer]

@IPA as Lisak1 said, I'll also let people who are better at construction answer those questions, but be sure to check out the Bog building topic if you haven't already. It may answer some of your questions, or at very least, give you ideas. I used that topic when I built my own bog. Without that topic and the people here who have done bogs, I would have had no idea what I was doing. I've had crystal clear water thanks to my bog.

 

[Meyer Jordan]

Has anyone used a downflow (water drawn from bottom) bog? What is the disadvantage of the downflow design?

In theory, a downflow gravel bed filter ('bog') will work as efficiently as an upflow or lateral flow. In reality, for use in a pond they are impractical, Organic debris will accumulate in the top few mm of the gravel resulting in a algae growth and severe clogging.

 

[Lisak1]

Organic debris will accumulate in the top few mm of the gravel resulting in a algae growth and severe clogging.

I would agree 100% with that. Our "down flow" bog gravel needs hosing down frequently to clear the finer debris that accumulates.

 

[Angel]

Welcome.

I have an up flow 100g stock tank bog set up and clear water and thriving plants. ( about 7,000g pond )From what i have read and investigated prior to my bog was up flow is for lack of better words 100% effective. While i have read maybe 1 down flow article per 100 on up flow being effective as well. ( i spent weeks looking hours on each search reading etc 2-3 times a day ) Seems to me down flow is a exact science / math / engineering.

So for lack of information on a down flow vrs up flow I went up.

I am still new to this form but I have grown to respect @Meyer Jordan as his answers are not a yes or no there is a explanation to it.

 

[Meyer Jordan]

Welcome.

I have an up flow 100g stock tank bog set up and clear water and thriving plants. ( about 7,000g pond )From what i have read and investigated prior to my bog was up flow is for lack of better words 100% effective. While i have read maybe 1 down flow article per 100 on up flow being effective as well. ( i spent weeks looking hours on each search reading etc 2-3 times a day ) Seems to me down flow is a exact science / math / engineering.

So for lack of information on a down flow vrs up flow I went up.

I am still new to this form but I have grown to respect @Meyer Jordan as his answers are not a yes or no there is a explanation to it.

The idea behind a 'bog' comes directly from engineered wetlands.Depending on the type of water that is being 'cleaned', they may be upflow, downflow, lateral flow, surface flow, or subsurface flow. These constructed wetlands are generally sized by acres not by square feet so clogging is not an issue of concern. As with anything, unless a new technology is used, when you downsize, you lose operating efficiency and capacity. One can't expect a Volkswagen Beetle to perform on the same level as a Rolls-Royce.

 

[IPA]

Thanks @Lisak1 @JBtheExplorer @Meyer Jordan and @Angel . I have been following the forum for a little while and respect the advice and knowledge here. I wondered if it was practical to build a downflow bog connected to an upflow bog with a pond and pump in between. I envisioned the intake or downflow to utilize a triangular wier and walls as separation, a kind of skimmer, where fry and tadpoles would have a home and larger fish could swim over the triangular wier as they pleased. I need to get my pond built so it will be a single upflow bog. I was just making it more complicated, probably because it is exciting to design an environment to support living breathing creatures. I watched a YouTube video where 2 floors of an apartment was a koi pond. He stated, "I don't keep fish, I keep water." I don't need anything so complicated and just need something as simple as possible I can build and install in a weekend. And by the way, famous last words, planning on only goldfish, not koi.

 

[addy1]

First set of questions is how deep should the gravel in the bog be, including the height of the PVC pipes or not? I have read 12" max (does that include the PVC height?) but also 18" to 24" to prevent the plant roots from clogging the pipes. Also, with the small size of the pond and bog I have read 1.5" PVC is okay, but would 2", 2.25" or 2.5" be recommended

Hi welcome!

My bog is 2.5 feet deep, mainly because I dug it that deep. Got tractor happy! I used 2 inch pvc, bigger is better in my mind.

 

[Meyer Jordan]

I wondered if it was practical to build a downflow bog connected to an upflow bog with a pond and pump in between.

Yes, you can but you may need two (2) pumps. Where will the water from the upflow 'bog' in this scenario be directed.

 

[IPA]

Yes, you can but you may need two (2) pumps. Where will the water from the upflow 'bog' in this scenario be directed.

The down flow would connect directly to the upflow which flows back into the pond which in turn flows into the down flow. It would all be contained in the same liner and maybe the compartments are not completely sealed off so that the system still works as water level falls.

 

[Meyer Jordan]

The down flow would connect directly to the upflow which flows back into the pond which in turn flows into the down flow.

That will not work. The outlet/outflow of any 'bog' is gravity driven. There is nothing pushing the water upward in the upflow 'bog'. The design that you are considering the downflow 'bog' will overflow before the upflow 'bog' is even partially full unless you are planning an extremely low flow rate in both 'bogs'.

 

[IPA]

@Meyer Jordan , when I said directly connected I meant not flowing back into the pond. The downflow is connected to the upflow with a pump. Anyways, I appreciate your feed back however it is also having the effect that I want to try it and unless you think there isn't any benefit to such a system even if engineed to function. Also, I'd use air stones to turn the water column, which I plan on doing anyway. Speaking of that, I am clueless on an appropriate air pump for a pond between 300 and 450 gallons. Most pond air pumps start at 1,000 gallons and I don't want the water churning so hard I can't see the things in it.

 

[Meyer Jordan]

The scenario that you are describing would work fine with enclosed pressurized systems, but in this case you are relying on gravity to supply the required water to the pump.
How are you going to get the water to the downflow 'bog' if the pump is between the two 'bogs' without adding a second pump?

 

[IPA]

The scenario that you are describing would work fine with enclosed pressurized systems, but in this case you are relying on gravity to supply the required water to the pump.
How are you going to get the water to the downflow 'bog' if the pump is between the two 'bogs' without adding a second pump?

The intake of the pump is pvc (or flex) pipe to a pvc distribution under gravel, the output is also pvc to a pvc distribution under gravel at opposite ends of the pond. The pump is used as if it were external, tubing/pipe connected to input and output, and it could be external, but it's just in the water because I like the no pipe leak worries of the pump and pipe in the water. Sorry I wasn't making that clear, I was thinking it, just not saying so.