It is well known the easiest way to clean out a sand and gravel filter is to introduce air.
Introducing Air Into Gravel Bog?
- Thread starter Dirty Dawg
- Start date
Sure, as part of a backwash cycle if I'm not mistaken. But A. we're not talking about a sand filter and B. we're not talking about backwash. The air dirtydawg is proposing adding would be flowing the same way as the water in the bog - upwards. So how would air disturb anything that the water wasn't already putting in motion?
Let me say it again - our bog has no solid debris that enters it from the pump. Most bog set ups that I have seen or read about are the same. They either have pre-filters installed or the water that is pumped through them are free of solid debris. So to me this is really a moot point. But you said it would be a problem so I'm just curious how you came to that conclusion.
fishin4cars
True friends just call me Larkin
I have to agree with Dieselplower. And it's quite easy to find out, leave the water running and stir up the gravel 10-12 inches down and see if brown particles stir up. If it doesn't I would be extremely surprised. Adding air may add oxygen to the gravel bed which would be great, problem is that then the gravel is no longer filtering the fine particles out of the water and it's not leaving it in the gravel bed for the plants to feed on. Also adding air is probably just going to add a channel where the air rises through the gravel and only add oxygen to a small area. Periodically adding air during backwashing may however benefit the bog to help loosen debris trapped in the gravel and help flush it from the system helping remove some load that the plants would be normally feeding on. I have not added air to my system and the bog holds 9 yards of gravel. I don't prefilter and I have not had any issues at all with negative bacteria colonies so far.
So Larkin, I'll ask you: Why would you assume the air would push up debris that the flow of the water wasn't already moving upwards? Would air create channels? Maybe, if the air flow was strong enough. But water could do the same thing, right? Moving water is a pretty powerful force if it's moving fast enough. You wouldn't want to blast air through your bog anymore than you would water - it would kind of defeat the purpose. But saying air flowing through the system would move debris but the water doesn't makes no logical sense to me. And I'm not saying it would be a positive thing either - it may just do absolutely nothing at all. We have an aerator in our pump vault to oxygenate the water. We assume it helps, but we would need some tools of measurement that we don't have to test the theory.
I have dug in my bog, lots of times - it's a part of my garden after all, so I plant and divide and clean up and re-plant in it on a regular basis. The sediment that is in my bog comes from the top - dirt and silt that the wind blows in and maybe some dirt that was still on the plants that I put in there. I have the same sediment in my shallow pool, and maybe to some degree on the pond bottom as well. The whole pond is open to the environment obviously so there's no stopping dirt or dust that settles on the water from accumulating.
Once I get down past that fine layer however my gravel is clean. There's no sediment, no debris, no muck, no smell. Just gravel and water. This idea that my bog is some kind of debris trapping muck filled toxic hole in the ground slowly poisoning the fish baffles me. I just wonder where those assumptions are coming from. And when I say it's not that way at all, the response is "well then it's not working". So if it's not a bad thing then it's not a thing at all? No way could it actually work according to some opinions.
When we were building our pond and stumbled on the idea of a bog filter, we searched and searched and searched for good information. There was none. We were lucky enough to visit a number of ponds that had been built or retrofitted with bogs so we had confidence that it would work. I just like to share that positive information with other people who may be in the same place we were at the beginning of our pond planning.
I have dug in my bog, lots of times - it's a part of my garden after all, so I plant and divide and clean up and re-plant in it on a regular basis. The sediment that is in my bog comes from the top - dirt and silt that the wind blows in and maybe some dirt that was still on the plants that I put in there. I have the same sediment in my shallow pool, and maybe to some degree on the pond bottom as well. The whole pond is open to the environment obviously so there's no stopping dirt or dust that settles on the water from accumulating.
Once I get down past that fine layer however my gravel is clean. There's no sediment, no debris, no muck, no smell. Just gravel and water. This idea that my bog is some kind of debris trapping muck filled toxic hole in the ground slowly poisoning the fish baffles me. I just wonder where those assumptions are coming from. And when I say it's not that way at all, the response is "well then it's not working". So if it's not a bad thing then it's not a thing at all? No way could it actually work according to some opinions.
When we were building our pond and stumbled on the idea of a bog filter, we searched and searched and searched for good information. There was none. We were lucky enough to visit a number of ponds that had been built or retrofitted with bogs so we had confidence that it would work. I just like to share that positive information with other people who may be in the same place we were at the beginning of our pond planning.
Yes.
I don't have a bog and, but I can understand how they work. They basically work in much the same way nature filters water through the Earth, but much like many other things nature does that we emulate, once we understand how it works we can often do it better. I've been studying the treatment of waste water and basically the whole science of waste water treatment is to do what nature does, but do it better. In every aerobic filtering process in the treatment of waste water one of the key elements is aeration, and lots of it. So I would have to say if you have filter process that involves aerobic bacteria, then yes, the more aeration the better.
Of course this may not change the deficiencies inherent in bogs, and that is that bogs are hard to clean out, though not impossible, and they are not particularly self cleaning like other types of filters (eg; shower filters, moving bed filters). But perhaps if you were to build it with nozzles or diffusers in strategic locations in your bog perhaps you could create a sort of self cleaning, or more accurately an automated mechanism for cleaning the bog.
I think if I was going to build a bog I would incorporate aeration lines in there for the small extra bit of trouble it might well be worth it. Besides, if it sounds like it might help improve something, and especially if it hasn't been done before, that's the sort of thing I would especially like to try.
Of course this may not change the deficiencies inherent in bogs, and that is that bogs are hard to clean out, though not impossible, and they are not particularly self cleaning like other types of filters (eg; shower filters, moving bed filters). But perhaps if you were to build it with nozzles or diffusers in strategic locations in your bog perhaps you could create a sort of self cleaning, or more accurately an automated mechanism for cleaning the bog.
I think if I was going to build a bog I would incorporate aeration lines in there for the small extra bit of trouble it might well be worth it. Besides, if it sounds like it might help improve something, and especially if it hasn't been done before, that's the sort of thing I would especially like to try.
Lets get this straight.... If you want the bog for mechanical filtration, adding air will decrease it's effectiveness. If you want the bog for biological filtration, adding air may help, but only if your water has a low level of dissolved oxygen.
That is the question isn't it. Like so many DIY filters in the backyard pond hobby, they are never sure exactly what function they are suppose to be fulfilling. Are bogs mechanical filters, or are they biological filters? Maybe they are like Skippy filters, meant to do one thing, but actually end up doing the other.
The truth is pretty much everything in the pond that gets wet fulfills the role as a biological filter, since nitrifying bacteria will grow on everything, including the plants and fish. So the rocks in a bog would make great surface area for bacteria to grow on. If a bog's only function is to act as a sediment filter, it would be a pretty poor one since they are hard to clean out. Most sediment filters have some sort of drain valve or something for removing the sediment once it is captured.
As for adding air only being useful if a persons water is low in dissolved oxygen, I don't think that is as straight forward as you try to make it. All of the most efficient biological filters (eg; shower filters, moving bed filters) are more efficient simply because they deliver more DO to the media and are self cleaning, or cleaned by the action of the air, as apposed to submerged media filters that are not exposed to the air at all and always completely submerged. They are more efficient not because the ponds they are used in have particularly low levels of DO, but because they are so efficient at concentrating the DO at the point in the system where you are trying to promote vigorous bacteria growth. So if that place happens to be a bog, then by all means do what you can to increase the DO levels there.
If your pond was low on DO you would be better off adding air in the pond rather than in a bog filter. The air will still make it to the filter, but without disturbing it.
fishin4cars
True friends just call me Larkin
I don't think adding an airsupply separate from the water flow would hurt at all. My issue would be adding air to the water flow. The air is only going to bubble up VERY close to the pipe, it's NOT going to disperse like the water does. so basically you would only be adding Oxygen to a very small area of the bog. I do feel like that adding oxygen to the pond itself and pumping hihly oxygenated water is the best direction. additional air supplied would be interesting to see how well it works. I don't know of anyone that has tried this and it's quite possible that it would work effectively. Inquiring minds would like to know????
Wow, huge difference of opinion regarding this topic!
As far as my expectations for the bog, I'd like to think it'd perform both mechanical and bio filtration. I really want to remove the inadequate filter mat that came with my Savio skimmer. With my pea soup situation still going, that filter gets clogged once a day. Even with my smaller 5,000gph pump in it instead of my 7,200 gph.
My initial idea for the venturi air introduction started when I decided I was going to instal an air-brake or whatever you want to call it to keep the elevated bog from siphoning back down into the pond if my pump loses power.
As far as my expectations for the bog, I'd like to think it'd perform both mechanical and bio filtration. I really want to remove the inadequate filter mat that came with my Savio skimmer. With my pea soup situation still going, that filter gets clogged once a day. Even with my smaller 5,000gph pump in it instead of my 7,200 gph.
My initial idea for the venturi air introduction started when I decided I was going to instal an air-brake or whatever you want to call it to keep the elevated bog from siphoning back down into the pond if my pump loses power.
You are exactly right. The air will go straight up and out, creating a chanel that is clean of debris (and restriction) so the water will proceed up through that area since it has the least resistance. This will lead to water that is not filtered well at all.
A bog will perform mechanical and biological filtration, but it is not the best method of doing either. The bacteria that convert ammonia and nitrite into nitrate (nitrobacter, nitrosomonas, etc) thrive in clean environments. If your have a bog that collects poop etc, it will gum up the surfaces of the rocks, causing the bacteria to operate less and less efficiently.