Pond Boss Forums POND CONSTRUCTION Creating habitat Pond biofilter question.

VERY early in designing the largest pond I think I can do on my property (6 acres but narrow w/ a flood plane)

I think I have decided that I want to build something using techniques similar to what this guy did.
http://kilk.com/pond/

I am planning on excavating hopefully around 12 feet deep in the deepest part. The overall deep part I am thinking I want around 20-25 feet wide and 30-40 feet long.

off of the VERY deep part I will put my dock, and it will gradually stair step up the longer part. the long sides will be a fairly steep angle.

Along both of the longer sides I am hoping to put around a 4 foot wide 3 feet deep (all gravel) area w/ a pipe in it to pump water up for vegetation on the sides and part of the bio-filter system. Off to the side of the stair steps at the shallow end I am thinking about building a massive gravel area biofilter.

How big should I build this gravel biofilter? I am thinking 15x15 and around 3-5 feet deep should be about right. this will be supplied by PVC pipe that flows water UP through the gravel which will then flow into the deep part of the pond and back towards the skimmer which will be hidden under the dock.

I am hoping for a waterfall feature which will also flow into the deep part. this will probably be closer to the shallower end and will be around 4 feet high and dump directly into the deep part.

I am looking pretty heavily at the helix pond skimmer.

Approximately what size liner should I use for this? or at least how do I calculate this. I will alter the size as needed in order to not have to try and seem two liners together.

what size pump will I need in the helix in order to push that kind of water through all that pvc.

are their any articles where I can read about how gravel filters like I am trying to do are constructed? I am sure I will have to reduce the pvc diameters as I move further out in order to keep the flow rates and pressures more even.

any other tips or ideas or concerns for me to do some more research on?

also, because of the depth will I need to aerate?
How would you expect the biofilter to behave in cold winters? should I shut it down to keep it from freezing over?

I have read a bunch about gravel biofilters just cant find anything that has been done on the scale I intend to do it.

Indygunworks,

I wish you the best of luck but you may not get much of a response as the pond type you want to build is nothing like 99.999 percent of the pond owners here. Virtually no one here uses biofilters for their ponds and instead use the natural biofiltration of much larger ponds.

What you want is more like a Koi pond. I think you might have better luck at a site like this:

http://www.koiphen.com/forums/

I realize its out there. I don't have a lick of clay on site so I think this is about my only option. Having plenty of fun learning about it though.

It's not really out there. Just that I'm afraid very few if any people do that here. I do know the koi people do a lot of this type of thing. Please don't run off. I just wanted you to be aware you might not get a lot of feedback on that here.

I tend to agree it's more like a back yard pond, no disrespect, as I have one too. There are a few differences in back yard ponds and country ponds. First is the bio/bog filter vs the "nature" bio/bog filter.

In the back yard system the best results are a crystal clear pond that runs through a Bio filter then through a Bog filter (pea gravel with plants, Ires) and back into the pond.

The Farm/Country pond is the same in idea but no pumps, fish shit in the water, algae/plankton/plants in and around the pond detoxify it and it goes around again.....Thus the pond is green, due to the plankton and Algae doing there jobs. And the plants are also trying to suck up all the nutrients they can at the same time,thus doing there jobs as well. All creating a NICE green pond, ;-)


Just FYI, the back yard pond guys say you need a bog filter 1/10th the size of he pond to keep it crystal clear, IF that is your intentions. I am not so sure about that as my BYP is about 1200 gal and I have a 1'x4' bog with about 5 iris, so not even close to 1/10th? But I do not feed heavy and try to get all debris out ASAP.

Hope this helps some?????

Rob C

At the risk of sounding negative, this is quite a project for even a professional pond builder, much less a homeowner.

That being said, here are a few items for consideration.

1. No need for a 12 foot depth. 5 feet is sufficient for a Koi pond.

2. You have not specified whether or not this will be a bare liner or Rock & Gravel pond. It will make a difference in the required size of the constructed wetland (gravel) filter.

3. For the proposed configuration, you will need at least 2 pumps and 2 skimmers.

4. Depth again. Constructed wetland filters need not be more than 1.5 feet in depth. This is the maximum root depth penetration that you will get from any desirable aquatic plant(There are some that you will want to avoid.).

5. 45 mil 'Fish Safe' EPDM liner is available in factory seamed sizes up to 200' x 50' Weighing roughly 0.30 lbs/sq.ft., EPDM liners can get quite heavy and require considerable manpower to install.

6. The size (volume) of any supplemental bio-conversion, biofilter or constructed wetlands, should be based on the projected ultimate fish load (weight) and not on the size of the pond. Keep in mind that the pond itself (total submerged surface area) serves as bio-filtration.

These are just a few items to consider in your proposed project. Much, much more would be involved.

I will be using it as a swimming pond and would like a majority of it to not be deep enough to touch. I have not decided if I want to line the liner w/ rock and gravel but my guess is it will be some combination of the above, but the areas where you can touch while swimming on the surface will probably be left to just the liner.

Ill be digging it w/ my 3 point backhoe attachment and using the dirt to fill the sandbags. I can double up the sandbags if needed as well, on set to create my couture and then line the rest of the the inside w/ another set of sandbags using actual sand or gravel. then if they get damaged I can just replace it with a new one. Rock would probably look better though.

if you don't have a large fish load, a few "growbeds" of gravel would work swimmingly
build a few "raised beds" around the pond that will act as your biofilter.. fill with gravel, drain back to the fish tank - you could run the growbeds "constant flood" where the water continously flows through the growbeds a few inches below the surface, or "flood and drain" with a siphon, pump always running
i've got over 100 fish in an 8' swimming pool, using about 600 gallons of gravel for filtration, growing lots of spices (basil, dill, rosemary etc) and some ornamentals (jade plants)