Can I add more that 12 inches of pea gravel to my bog filter?

[Kidsgardener]

This is my first post. I am building a wetland bog filter. My first layer at the bottom of the bog filter will be an underlayment and then a rubber liner then 11 inch tall milk crates, then I will put a 1/8 inch plastic hardware cloth over the milk crates and then a single layer of 2 inch river rock stone and then 12 inches of pea gravel. Total height would be 25 inches. My question is that I would like to add more pea gravel to raise the level of the bog to 31 inches, but all i have read said that 12 is the magic number for pea gravel depth.I read that above that will lead to bog failure. Is this true or can I add 6 extra inches of pea gravel without an issue?

 

[Jhn]

welcome....No, you can go deeper there are many of us here, myself included that have bogs with pea gravel much deeper than 12”.

Also, you are going to want to put underlay over the liner as well, and sandwich the liner, so it goes underlay, liner underlay then milk crates. You don’t want any edges from the milk crates tearing the liner with all that weight pushing down on it. The hardware cloth is unnecessary as long as your rock size graduates up, I used 8-12” rock over the aqua blocks, then 2”, then about 18-24” of 3/4” pea gravel in my wetland filter.

 

[Lisak1]

I agree with @Jhn on all points - deeper is definitely fine. Our bog is four feet deep, although the bottom is Aquablox, but we have more than 12 inches of rock and gravel. I don't know who the expert is who deemed 12 inches of gravel to be the magic number, but the experiences of many here have shown that you're working with a concept, not a formula.

I would also avoid the hardware cloth - its not necessary and will only create a potential for clogging down the line.

 

[Kidsgardener]

Thanks jhn... I will add that extra underlayment as a precaution and I appreciate your information on the pea gravel too.

 

[Kidsgardener]

Thanks Lisak1 , I wondered about the clogging factor..

 

[Kidsgardener]

Thanks Lisak1 , I wondered about the clogging factor.. I have some concern about using the milk crates collapsing with too much gravel above. I will be able to drain the area under the milk grates so I am hoping that will prevent any clogging of the 1/8 inch hardware cloth.

 

[Lisak1]

I share your concern about the milk crates - they aren't really designed for this purpose. But I do know people have used them without any issues, so hopefully It will work for you. Are you assuming the hardware cloth will help with the excess weight?

 

[Mmathis]

Hello and welcome. Twelve inches is just a suggestion, but deeper is better.

 

[Kidsgardener]

I share your concern about the milk crates - they aren't really designed for this purpose. But I do know people have used them without any issues, so hopefully It will work for you. Are you assuming the hardware cloth will help with the excess weight?

the hardware cloth will not in itself reduce weight load but it will replace the need for additional larger size gravel below the pea gravel to prevent it from falling through the crates.

 

[Kidsgardener]

Hello and welcome. Twelve inches is just a suggestion, but deeper is better.

Thanks Turtle Mommy.....I am going to use my pond as a rehab pond for injured turtles

 

[Lisak1]

Ah... gotcha. We used what they call geo-textile in our down flow bog for that reason. Covered the larger boulders with it to keep the gravel from filling the gaps. It's worked fine. I think that had one inch squares if I remember correctly.

 

[Kidsgardener]

I agree with @Jhn on all points - deeper is definitely fine. Our bog is four feet deep, although the bottom is Aquablox, but we have more than 12 inches of rock and gravel. I don't know who the expert is who deemed 12 inches of gravel to be the magic number, but the experiences of many here have shown that you're working with a concept, not a formula.

I would also avoid the hardware cloth - its not necessary and will only create a potential for clogging down the line.

here is the information that I found online
o here are the top 9 mistakes made construction bog gravel filters:

1. Too deep a bed of gravel – this is the most common mistake made, you need no more than 12” of gravel substrate. If you are adding a Gravel Bog to an existing deep pond area; construct a false bottom using grating.
2. The bog is too small: For water gardens 10 – 15% of surface area should be bog, and for koi ponds there should be 25 – 30%.
3. Wrong size gravel – use 3/8” pea gravel. Period. End of story.

 

[addy1]

The rules are what has been written up by somebody at sometime. Mine is 2.5 feet deep, big, pea gravel, full of plants.
I do nothing to it except groom excess plants.
I can do nothing to my pond all summer and it does great.

I have no clean out pipes, nothing underneath, ie crates, aqua blocks etc, the gravel is right on the liner, it has never clogged up in the ten years it has been running.

Crystal clear water, very little algae, never green water in the spring, minimal string algae, healthy fish, tads, etc.

So this period end of story is not the period end of story.

Welcome to our forum!

1. Too deep a bed of gravel – this is the most common mistake made, you need no more than 12” of gravel substrate. If you are adding a Gravel Bog to an existing deep pond area; construct a false bottom using grating.
2. The bog is too small: For water gardens 10 – 15% of surface area should be bog, and for koi ponds there should be 25 – 30%.
3. Wrong size gravel – use 3/8” pea gravel. Period. End of story.

 

[Kidsgardener]

Thanks Addy1 you made my Day! I have heard great things about you. My pond is about 100x60 x6 Ft 225,000 gallons spring fed and the bog i am making is 40x 15 ft ...by 30 inches....
i live by your motto

Live every day as if it is your last, enjoy it to the fullest, because one day it will sure will be.
Thanks to all that contributed here..I am excited to proceed forward today...!

 

[addy1]

i live by your motto

lol I am a "lazy" ponder, keep it simple! I built it with that in mind and it has worked better than I thought it would.

The main thing I do is pull the pond water from about a foot off the bottom of the pond, therefore you don't suck in leaves plant debris etc.
I used to clean the bottom of the pond, quit after doing it for a few years, there was never enough stuff to clean up.
I don't cycle the water at the rules level ie twice a hour, once a hour, I cycle about every two hours, works great. My pump is external It does need to be pulled in the winter.

The only thing I have to keep a eye on is water level, when we hit all the 90 plus days we had this summer, those bog plants suck up that water. I have a sprinkler system I use to auto water the pond, start at about 15 minutes a day (spring) up to a hour a day, dead of summer.
We are on a well so it is slow flow vs city water pressure, like 3 gallons a minute or so.