Lets talk UG filters

Discussion in 'Biological/Natural Filtration and Deep Sand Beds' started by Paul B, 25 Aug 2011.

  1. Paul B

    Paul B

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    Lets talk about Undergravel filters, no really. Old technology? maybe but so is running water. When we got tired of going outside to pump water, we didn't stop using water . We invented faucets. OK not a great analogy. In the beginning of the aquarium hobby, which was right after WW2 we all kept goldfish and guppies. The first thing we did was to put in an undergravel filter, why? Because it worked. Originally we thought it was a mechanical filter and we loved mechanical filters because we liked to filter out particles. Water quality didn't matter as long as we could see the fish. Clear water was also essential to locate the dead fish, and we found a lot of dead fish.
    Not because of the UG filter, but because we were using it wrong. We read the instructions and that was our first mistake. The people who invented and sold UG filters were not at fault, they also liked to filter things and an UG filter does that fairly well. Unfortunately, for some reason we didn't want to think of all that stuff that was filtered but still in the tank. We must have been busy watching those Ann Margaret movies.
    But in our defense, freshwater systems do great with UG filters. I am not sure why but they do.
    Then we all got high class and changed most of our systems to salt water. We loved our UG filters so we kept them, after all, they worked great and "filtered" out all that "stuff" that we figured we needed to filter. Then there was Bonanza on TV and we again forgot that an UG filter does not remove anything.
    Boy were we stupid. Thats when 99% of us removed the UG filter. But there is something I like to call those people, and that is "wrong".
    The UG "filter is fine, we were the problem. It is not a "filter" even though that is what it reads on the box, it is a water treatment system.
    If we use it as a filter, our tanks will crash, guaranteed.
    Robert Straughn (The Father of Salt Water fish Keeping) advocated UG filters as the greatest invention since tap water. The man was a genius but he didn't know the reason the UG worked.
    The UG "System" will only work if we keep out the particles or as we like to call it "detritus" (dirt, crud, shmutz etc.) The gravel on the bottom of a tank vastly increases the real estate that bacteria can live on. Bacteria are like us, they like water front houses with continous fresh calm breezes and lots of easy to get food. Gravel is perfect for them and, like apartment buildings, they can live on top of each other without getting in each other's way.
    Water with no particles flow past those bacteria, the bacteria process out what they want, which depending on the type of bacteria that could be nitrate, nitrite, ammonia
    or Harvey's Brystal Cream. Too many particles and the bacteria will think they are living in a slum and the water flow along with their oxygen and food will stop.
    Some bacteria are lucky and they like it when there is less oxygen, they have larger noses to collect oxygen, maybe not, I don't know, but they process nitrate in the absence of oxygen.
    So some detritus in the gravel will limit oxygen and actually help those bacteria convert nitrate and detritus is going to get in there no matter what we do.
    The best way to run a system like this is to take the UG filter and throw out the instructions. Then build a manifold above the water. Connect the tubes from the UG filter to the manifold and pump water into the manifold so all the tubes get a slow even flow. The water going into this manifold should first be strained to kep out those large smutz particles. Run this arrangement slow. The slower, the better.
    Will this run for fifty years with no maintenance? Absolutely not. A few times a year you need to stick a canister filter of some type in there and stir up the gravel. It helps if most of the rock is not laying on the bottom. That doesn't look good anyway so figure out how to do a dynamite aquascape job.
    It may get you a girlfriend, maybe not. :whistling:
     
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  3. RiaanP

    RiaanP Moderator

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    nicely put.
     
  4. Midasblenny

    Midasblenny

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    hehe, you make good points, what are your views on the reverse flow method which was introduced some time later and is still used by some freshwater hobbyists?
     
  5. Paul B

    Paul B Thread Starter

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    Last edited: 25 Aug 2011
    Tremayn likes this.
  6. Tremayn

    Tremayn

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    Very interesting! Thanks :) .. <click>
     
  7. RiaanP

    RiaanP Moderator

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    Ok, my opinion only.

    Reverse underground filter can work. Basically its just an enormous surface area for bacteria to live on. Any surface will do, as long as there are some flow past it. Having slow constant flow, that would help with the processing of nitrate in the absence of oxygen.

    Same as what is claimed on NP-reactors. I mean, how can a NP-reactor do the nitrate part if you pump a lot of new fresh oxygen loaded water into the chamber? So in essence, you have a big NP-reactor. And that is the key. The water needs to be able to move through the substrate (or pellets) for the filtration to be able to work. Pump too small, and you will not be able to push the water through the sand (or pellets). To much flow, and your substrate will "boil". In a NP-reactor, the pellets collects and block the top at the mesh outlet. Both your reverse UG and the NP reactor have one big issue that must be sorted. You do not want to pump any bigger detritus particles into either. So a pre-filter is an absolute must. Even a simple solution as what you got.

    Some other thing to ponder about. The success of a reverse UG filter will greatly depend on the particle size of your substrate. Sand or sugar fine aragonite will not work. firstly they will fall into the filter system. To prevent that a fine mesh is needed. And that will block up easily with detritus.
    So you must have substrate that is big enough not to fall into the slats of the filter. As in this picture of your system, you obviously use bigger grain particles.

    [​IMG]

    Lastly, the opposite from a pump that is too weak, is a pump that is too strong. It will blow open some areas, like a mini volcano. Where it will allow to mush flow to exit. And then the other areas will not get enough flow and then the same issues will pop up as in a pump that is too weak. And the bigger the UG filter, the more pronounced this issue will be.

    This is all just my opinion. Maybe I got it wrong, and Paul B with a lot more experience could lead me into the right direction.
     
  8. belindamotion

    belindamotion Google Master

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    I'm tagging as I love the "old school" ways...
     
  9. dallasg

    dallasg Moderator MASA Contributor

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    i ran my first tank years ago with a reverse flow UG filter with "inverted" powerheads and a air-driven skimmer for 5 years

    even with a UG there are slow flow areas which would help some what with nitrate reduction, i then supplimented this with a home made nitrate reductor, which was even more magical
     
  10. Braco

    Braco

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    Interesting topic tagging along...:whistling:
     
  11. Paul B

    Paul B Thread Starter

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    No, you didn't get anything wrong. It is all correct.
    A RUGF actually depends on some detritus to reduce nitrate and will not function for 6 months or more as a viable nitrate reducing method. No matter what you do, the interfaces of the gravel where they are touching will become packed with detritus. This will reduce the flow in between every gravel grain. These tiny places are tiny to us but to a bacteria they are an entire village and there is plenty of room for a anerobic bacteria to find a home where there is reduced oxygen. That is the reason for the very slow flow. A DSB works for a while because water can get to the bacteria in the oxygen depleted lower areas but eventually those areas will become compacted with dead bacteria, pod shells etc and no water will be able to penetrate. No water means no nitrate reduction so the thing fails. Those "creatures" that are supposed to dig down to make water channels do not re produce forever and they will not dig down to an area where there is no oxygen. That is the problem with DSBs. If you run a RUGF long enough , it will almost become a DSB. Well not quite but you know what I mean.
     
  12. belindamotion

    belindamotion Google Master

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    @Paul_B Is it possible...when you have the time...to start a Thread about erecting a Reverse Underground Filter..the proper way, as you have mentioned that some of the "current" RUF Articles are not done properly... I'm very interested in the RUF, but can't get info and have NO IDEA how to set up something like that...as I'm looking at doing RUF with an Algae Scrubber...next and final upgrade...
     
    Last edited by a moderator: 26 Nov 2015
  13. Paul B

    Paul B Thread Starter

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    I will try to get to that but if I forget send me a PM
     
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