Under gravel filtration and air diffusers?

[Priscilla]

I think my friend has a grid of pipes all over the bottom of his pond, covered by rocks, the pipes are connected to a pump that pulls the debris through the holes drilled in the pipes. It seems like a great idea to me. You're constantly sucking that stuff out. His pond is 6 feet deep, so perhaps that's why he did it? I don't know. The debris then goes to mechanical and biological filtration.

Now that I think about it - there maybe sand some where in that equation too .... ?

He's an older guy, so maybe that's the way they used to do it and he just stuck to it ... ? He's been ponding for many years. Not an internet kinda guy, so maybe the new stuff missed him.

It does seem to work of him.

I will ask and get some more details.

 

[sissy]

It would be a 1 time thing but that one time would have to be watched closely unless you did it while building the pond .I do have 2 pipes at the bottom of my pond on a pump and they have holes drilled in them .I saw it on you tube and figured give it a try ,but i don't have rocks in the bottom of my pond .I just figure it would keep the bottom of the pond from collecting all the poop from the fish .I even thought if it did not work I could always put a pump on the 1 end and suck some of the dirty water from the bottom of the pond along with fish poo .Bottom seems clean but as I said there are no rocks down there.Plus my pond was new when I put it in since I had to rebuild it .

 

[HARO]

Under-gravel filtration was touted as THE system for ponds, back in the late 50's and early 60's. When the pond went out for a few hours, people would lose all their fish! It seems once the water stops moving, the whole thing turns into a SEPTIC TANK! These systems are not used today for that very reason!! BTW, I knew one pet shop owner who was away at a convention when he got an urgent phone call saying that his large air pump was no longer working and that he had several dead fish. By the time he got there, he had lost every fish in the tanks serviced by that pump. All were fitted with undregravel filters! He used to swear by them.... now he swears AT them!!
John

 

[Mucky_Waters]

I see that people are starting to use 2" pvc piping with drilled holes in it on the bottom of the pond to filter the the rock bottom.

Where are you seeing that?

 

[JohnHuff]

Where are you seeing that?

The 1950's and '60's.

 

[dieselplower]

Maybe it was in a Back to the Future movie hahaha

 

[Mucky_Waters]

I've had many aquariums with under gravel filters. I think in an aquarium with gravel on the bottom they are a really good idea to have at least as supplemental filtration system, and if the fish load is low they might be all that is necessary. However in a pond setting I don't think they are a very good idea, especially when substituting fine gravel with rocks. There can be a lot of differences between ponds and aquariums, the least being the amount of debris that might accumulate in a pond as opposed to an aquarium. If a fish dies and sinks to the bottom of a gravel bottom aquarium, very likely someone will notice it and scoop it out. In a pond that fish will likely slip between the rocks on the bottom of the pond and never be noticed, there it will sit until it completely decomposes, meanwhile adding large amounts of ammonia and nitrites, and other nasty things to the pond water. Also, most people who keep gravel bottom aquariums vacuum their gravel once in a while to clean it of excess debris, but that would be hard to do effectively in a rock bottom pond, since first of all it's a lot harder to see what you are doing, and second, because rocks have much bigger gaps the debris would sink farther out of reach and any vacuum would have a hard time reaching down in those cracks.
All that being said, just about any method of circulating pond water will help establish a nirifying bacteria colony of the pond surface, rocks, plants, fish, hair curlers, bio-media, etc... Beyond that it's just a mater of how heavy your fish load is? how clean do you want to keep your pond? and how much extra maintenance do you want to do?

 

[dieselplower]

All that being said, just about any method of circulating pond water will help establish a nirifying bacteria colony of the pond surface, rocks, plants, fish, hair curlers, bio-media, etc... QUOTE]

True however those bacteria function best in a clean environment with high oxygen levels. Poop filled rocks at the bottom of a pond are not an ideal place for them to function effectively.

 

[sissy]

Mine was not put under gravel in my pond it was done to mix new water with all the old stored pond water I drained out of my leaking pond .I needed to get it done fast between 2 snow storms and fish in 2 temporary stock tanks .I liked the way it really moved water at the bottom so I kept it in place .It really helped melt all that snow in the pond .I also shoveled the top layer of snow outside the pond into the pond .I did not want to over work my new well pump .Cost to much to pull it up 400 ft and did not want to pay out that kind of money again .I use lava rock and they consider that old fashioned ,but if it works why fix it .I'm old and no complaints here yet

 

[Mucky_Waters]

True however those bacteria function best in a clean environment with high oxygen levels. Poop filled rocks at the bottom of a pond are not an ideal place for them to function effectively.

Actually it can be, as long as they are getting a continuous supply of oxygen. The good (aerobic) bacteria needs three things, the right temperature, nutrients (poop) and oxygen. As long as the temp is right and they get a steady supply of those other two things the will flourish. But as Haro pointed out, the problem arises when oxygen levels drop, the good (aerobic) bacteria dies back (or goes dormant), and the not so good (anaerobic) bacteria start growing and producing H2S and methane gases. Which is what Haro referred to as septic conditions. The anaerobic bacteria that thrive in an oxygen free environment are also nitrify bacteria, they just do it differently, and because they also produce H2S and methane gases they are not desirable in a fish pond.
An ideal filter will have some way of collecting debris (leaves, poop, dead fish, etc..) in a way that it can be easily removed from the pond environment before much of it has to be "digested" by bacteria. If you could remove 100% of the debris like that you could get away with a minimal bio-filter that would only have to deal with the ammonia excreted from your fish. This is the biggest failing I see with under gravel (rock) filter in a pond, in that you have no effective way of removing much (if any) of the debris before it gets sucked into the rocks, so you have to depend on your bacteria colony to digest 100% of the debris that might accumulate in your pond. This is where I don't see much difference between a bog and an under gravel filter, except that maybe a bog might have some sort of pre-filter that can be periodically cleaned out.

 

[dieselplower]

I dont believe the aerobic bacteria eat poop. They convert ammonia and nitrite into nitrate. Not exactly the same thing. These bacteria need clean water. That is why a biofilter is always suggested to come after a mechanical filter.

 

[Mucky_Waters]

I dont believe the aerobic bacteria eat poop. They convert ammonia and nitrite into nitrate. Not exactly the same thing. These bacteria need clean water. That is why a biofilter is always suggested to come after a mechanical filter.

You may not believe it, but that's exactly what they do. We are talking about a biological process, not just a chemical reaction.
Much of what you remove from a mechanical filter could eventually breakdown and also get digested (eaten) by those same bacteria, however it would take a lot longer, put extra demand on the biological process, and the solids could foul up and clog the bio-media, what ever that might be. That's why we try to mechanically filter out as much of the solids as we can before sending the water to the bio-filter.

 

[JohnHuff]

This is where I don't see much difference between a bog and an under gravel filter.

As WB said in the thread on the other forum, the bog is one of the worst types of filter for water. The only redeeming point to me is that it's a plant feature and people build them for the plants and not their fish.

 

[sissy]

odd then how come so many people on this forum have bog filters and the seem to work .Why would any filter really work .Mine has plants and has lavarock and it seems to work also .

 

[JohnHuff]

odd then how come so many people on this forum have bog filters and the seem to work .Why would any filter really work .Mine has plants and has lavarock and it seems to work also .

This is a good explanation from WB: http://forums2.gardenweb.com/forums/load/ponds/msg0613005022283.html?53

Also from WB: http://forums2.gardenweb.com/forums/load/ponds/msg0709183823247.html?18&rnd=tjMpK