Bog filter gut check before construction

[twoheadsbrewing]

Great info, thanks everyone!

 

[twoheadsbrewing]

I'm going to start the build; digging the bog, trench for water line, and adding a tee at the skimmer and backflow/ball valve.

Here's what I'm planning, just not sure if the bog is big enough with the gravel that will go into it. Pond is about 600g, bog will be 60g before the gravel. Your thoughts?

 

[poconojoe]

I'm going to start the build; digging the bog, trench for water line, and adding a tee at the skimmer and backflow/ball valve.

Here's what I'm planning, just not sure if the bog is big enough with the gravel that will go into it. Pond is about 600g, bog will be 60g before the gravel. Your thoughts?

View attachment 139434

As a general rule, the bog's surface area should be at least 30% of the pond's surface area.

 

[Jhn]

What @poconojoe said surface area is more important than how much water it holds. So you are maybe a bit undersized with the bog but not too far off, so it should be fine.

 

[Lisak1]

100% agree with the surface area being the most important factor. You'll want to fill that thing with plants!

 

[twoheadsbrewing]

As a general rule, the bog's surface area should be at least 30% of the pond's surface area.

Good to know, thanks! I do have some more room to extend it up to 5 feet which should come close to 30%.

 

[GBBUDD]

Pumping to the bottom of a bog and forcing the water upward if a water fall is not in the design coming out of the bog is a wasted opportunity and energy source. if the bog is off to the side of the pond i would just make a shelf like @addy1 built with a raised wall between this way the entire side of the pond can have planted marginals etc. this can also break up the round man made look to a pond

 

[twoheadsbrewing]

Pumping to the bottom of a bog and forcing the water upward if a water fall is not in the design coming out of the bog is a wasted opportunity and energy source. if the bog is off to the side of the pond i would just make a shelf like @addy1 built with a raised wall between this way the entire side of the pond can have planted marginals etc. this can also break up the round man made look to a pond

Yes, there will definitely be a waterfall along that between the bog and pond. I'm going to build up a dirt wall a few inches to force the water from the bog to come up 4-6" above the surface of the pond.

 

[combatwombat]

@poconojoe / @Jhn / @Lisak1: Why is surface area more important than volume? Would think more volume = more surface area for bacteria = more ammonia conversion.

 

[Lisak1]

I already answered... more plants! haha! But for real - the more surface area you have, the more plant action you can have going on and that's a big part of the function of a bog.

Actually the surface area is directly related to volume if you follow the standard formula for depth. I personally like a deeper bog as it allows for more DWELL TIME (its firmly in my brain now!) but the "standard" recommendation is 12 - 18". I'm sure someone at some point did the math on that and decided 30% was the "ideal" size.

HOWEVER... the very first bog I ever saw in person was four feet deep and about 2 feet by 2 feet at the surface - and it worked great. You could barely tell it was there. Many ways to skin the proverbial cat.

 

[Jhn]

@poconojoe / @Jhn / @Lisak1: Why is surface area more important than volume? Would think more volume = more surface area for bacteria = more ammonia conversion.

Because it’s not just about SSA for bacteria in a wetlands filter, the larger surface area enables the ability to add more plants, which are every bit as important in maintaining water quality.

Haha @Lisak1 had same response

 

[combatwombat]

@Lisak1 / @Jhn: That makes sense. I've been testing my knowledge on the nitrogen cycle the last few days and realizing there's a lot more to it than just ammonia / ammonium --> nitrite --> nitrate. Started thinking "What's the point of the plants? They just eat nitrates, which are not much of a concern for water quality." And, on that, started thinking surface area for plants doesn't matter that much because the conversion of ammonium and nitrite is what matters.

But then I learned that plants actually prefer ammonium and only take nitrates if ammonium is not available. And then I forgot that I learned that and asked you why surface area for plants matters.

 

[Lisak1]

There are people on both sides of the "which is more important" fence - the gravel or the plants. I'm sure if you got all science-y about it someone could make a final determination as to ULTIMATELY which provides more benefit to the pond, but obviously "more important" doesn't mean "unimportant". And luckily "both" is a really great choice, so there you go!

Honestly though, more surface area means more plants which means more variety, which is also key. Plus it's pretty! I love planting in my bog - I'm always trying different things to see what works, what I like, what I don't. And the next year - try something new. I do have plants that come back each year, but I've learned to limit those to things that are easy to manage. The big stuff I use annuals - much easier to get rid of after one season!

 

[addy1]

There are people on both sides of the "which is more important" fence - the gravel or the plants.

Both! I have lots of gravel and lots of plants!

 

[brokensword]

You also increase oxygenation with more surface area. They are directly related.