Up-flow bog filter vs down-flow bog filter

This is just a short video why i try and make sense of my preference for up-flow bog filters as opposed to down-flow bog filters.

In the video I briefly mentioned the role of bacteria in keeping a pond clean, clear and healthy. Here is a good video that explains that in more detail, yet still beginner friendly -

[paullill]

Can I just say a massive thank you, after watching your videos I built my mum an up-flow bog filter earlier this year after she had been struggling with green water for years, after a month of being used she has had so many comments on how clean the pond is you’ve saved hours of work and added hours of enjoyment

[stefanovanenio]

I have a 20 foot by 15 foot pond that is about 5 feet deep and crystal clear water, I mean when I drop my gopro in it doesn't look like there is water at all, just a load of flying koi, this is completely down to a bog filter. I took inspiration from oz ponds! I do though, harvest rainwater and drop in 3-400 gallons in every week or two. I have calculated the cost of the bog filter including plants to around £1200. If I were to use an off the shelf filter with UV etc I would have been looking at £2500minimum. Plus I get massive satisfaction at creating my own little ecosystem. Thanks Oz ponds!!!!

[kenmcguire]

This is by far the best channel for home built ponds. I have designed my plan based on everything I learned here.

[TheDrillMaster]

We have a large pond here in Florida and it's constantly green/brown. I have worked hard to learn how to eliminate the massive algae buildups we would get throughout the summer and I seem to have accomplished that with a rather crude setup that I want to expand. I learn everything from watching your videos. Thank you so much.

[sweeyong]

My experiennce wtih upflow filter is the sediments builds up in the media over time in the pea gravel. . Just an update it took almost one week, 8 people to manual clean out my bog filter. Its got large river stone about 10cm thick, course gravel about 10cm, and pea gravel 20-30cm in a 4 meter diameter upflow bog.

So now eveything cleaned out, plan is to have 5cm -8cm worth of pea gravel, to make it easier to clean out the sediments. Pipe the water a prefilter (mechanical) before entering the bog.

Its going to be an experiment to see which works best.

At the end of the day, there is always going to some sort of maintenance. Nothing is maintenance free.

Cheers.

[PYGolf]

Omg when that "oh damn I'm going down the rabbit hole" feelings kicks in

[karlroyston]

I think your theory on pond filters is spot on, im currently using a down flow, with pump in the pond returning to the bog filter and being distributed using a 12ft spray bar. I have had this pond running for 5 year's and the only maintenance has been removing the autumn leaves . Mu pond is 5 thousand gallons of which 2 thousand is bog filter, 8 x 16 inch koi live happily, I've never changed the water only topped up in the summer due to evaporation.
Karl from Ireland

[marnez]

I think the earth purifies the water from the same upward method, so this definitely makes sense. 👍🏻 Thanks for sharing

[praveshgaire]

the water glass example made it so clearrr

[allysonh]

I so wish I could understand this but I’m convinced you’ve got it figured out!! One of these days I’m gonna have a small creek through my backyard emptying into a small pond so I’m gonna keep watching till I figure it out 😊🙌🏻
Your Dream Pond is Gorgeous!!! Would love to see more of it
Great job!!! Thank you!

[the_bloke_that_cuts_the_grass]

I’d say your upflow system seems to work pretty well what I can see.
I love watching your videos, the sights and the sounds are mesmerising ❤

[doorvip]

Both my bird bath and container fish pond have been loving the upflow wetland/bog filter system.

Bonus is the pump sucks up mosquito larvae and I have my bog filter flowing out into micro mesh netting. I then feed the fish with the catch

[elmerkilred]

Bottom flow going up seems to be the least complicated to build, and maintenance. I clean mine once every five to six years, only because once the vegetation has established itself, it becomes a serious workhorse for filtering. The entire filter is about 2' to 2-1/2' deep (60cm to 76cm) 2" (5cm) slotted pipes are fashioned along the bottom into a shape that runs the contour of the pond with one intake, and about a foot (30.48cm) of 3" (7.62cm) gravel is filled over the top of the piping leaving about a foot of water for plants to populate the gravel. This bog makes it convenient for dechlorinating municipal water when added to the pond though aeration, and addition of dechlorinator, and in my hardiness zone the plants are the first up to start filtering when the bacteria is still in suspended animation from extreme cold winter temperatures.

[inaecht]

I just built a temporary up-flow bog filter with a bucket in an old flower pot and some pieces of a garden hose.
When I'm sure, the pot I used is big enough for our sun exposed pont, I will build a more beautiful one with plants and a nice bubbly overflow. I am really curious about the progress! But looks like just one night was enough to clear the water a bit.

Thank you for the inspiration and your explanations, especially on the diversity of possible methods.

[Jerbs]

From my personal experience:
Down-flow (input from top, output at bottom): output has to exactly match input.
- If output < input, bog filter will overflow.
- If output > input, bog filter will be empty.

Once the filters start to clog, output (top to bottom) will decrease and unless managed (i.e. clean filter or reduce input), the bog filter will start to overflow.

Up-flow (input from bottom, output at top): easier to manage as output cannot exceed input.
- If output < input, bog filter will overflow.
- If output > input, bog stays full and output flow matches input

Once the filter starts to clog, the flow to output (bottom to top) will decrease, causing input to decrease. Bog filter will not overflow.

[DarrinsDaffs]

As always, Kev, many thanks for your straight forward explanations! I continue to work (on paper) on my up flow bog for my 100 gal. koi stock tank.

[marcuscooper]

Cheers dude 😀

The only additional point I would make is that I think the top-down filters are far bigger because they use a lot less pressure, which I assume means they need a greater volume of slower-moving water to pull from.
The choice seems to be clear... if you don't care about streams and waterfalls, and want the cheapest to run swim pond, then go for top-down filtration with bubble tubes. If you want a stream or waterfall then you have to have a decent pump, which means you can save some space and go for a bottom-up filter, which can be crafted to add to the look of the whole design.

My next question is concerning how the water moves, as you showed with the glass and the tap (I'm convinced the power of the flow would send all the new water swirling to the bottom - you could have added some cordial and made squash to show how the water moved).
Anyway... without some sort of deep level powerhead, wouldn't the water come down a stream, hit the pond at a slightly higher temperature, go straight across the top and into the bog filter, and back round again? You'd just end up filtering the top few inches of water over and over, whilst the slightly colder main volume of water in the deep area never moves? I've seen ponds with additional jets and they make sense, but I've also seen some Aquascape creations that don't seem to have anything but the wetland and stream.

[fossphur]

I think it’s definitely easier to wash an up flow filter using gravity to backwash, than to somehow force water up through a down flow filter to flush it and unclog it. I haven’t needed to do this with my upflow bog filter yet since I ended up putting a chunk of foam over my pump to stop it from sucking up the frogs that insist on living in my skimmer box. I have a space to remove wastes from the bottom of the bog but so far it looks very clean (no solids). The battle with hair algae is still ongoing, I think I can remove it faster than it grows apart from the fact that it is chock full of tadpoles so I need to be very careful and only pull out small pieces at a time so I can check and return any inhabitants to the water. I don’t know if they eat it or if they are just grazing on the massive surface area it provides.

[disartdisart]

Love your content and the way You explain it! Best Regards from Bolivia

[CrisAnderson]

I just watched a video where a guy claims these pools cost around $5k a year in bacteria after each season.

I like your approach much, much better. There's any number of videos where they say they are virtually free to run...and this seems to be much more logical to me. I used to run a 300gal planted fish tank. The bio load and water volume were well matched, and I used a LOT of plants, and plenty of scavengers (pleco's, crawfish, shrimp, etc). But I found the real secret was simply over filtration, and a LOT of flow. I often wonder how that will work when I transition my experience to a natural pool/pond.