How does an undergravel filter work???

there's basically a flat panel that sits under your gravel. From that panel there is a tube that runs straight up and is usually connected to a powerhead or something like it. It does what the name says. It's an undergravel filter. It basically takes the debris from under your gravel and sucks it out through that tube that is connected to your powerhead and shoots it out where your other filters will catch the debris.

It's not very efficient and pretty useless. Just vacuum your gravel each time you change your water and you should be fine.

Without it, it's a lot less trouble =)

Not exactly...what an underground filter does is pull the debris down into your substrate...it does not throw debris into the water. Water changes are just as important when using underground filtration...think of it as rinsing your filters sponge if you will I find them very effecient...and even run one of my tanks with nothing but an undergound filter, and it does beautifully. It does make it way more difficult to clean in the long run, as every 6 mos. or so you have to completely break them down, as they will get very gross underneath eventually and won't work as effeciently. This is sa major hassle. I find that the tanks I have that I use underground in conjuntion with my regular filter do best.

luvmyfish said:

Not exactly...what an underground filter does is pull the debris down into your substrate...it does not throw debris into the water. Water changes are just as important when using underground filtration...think of it as rinsing your filters sponge if you will I find them very effecient...and even run one of my tanks with nothing but an undergound filter, and it does beautifully. It does make it way more difficult to clean in the long run, as every 6 mos. or so you have to completely break them down, as they will get very gross underneath eventually and won't work as effeciently. This is sa major hassle. I find that the tanks I have that I use underground in conjuntion with my regular filter do best.

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That's way way too much trouble in my opinion.

Here we go again.

An undergravel filter is no more work to maintain than any other tank with substrate. It requires good vaccuming, if run in the conventional set up.

If set up in reverse flow it virtually eliminates vaccuming, and works as well or better than any other filter format available.
Either way it would be rediculous to break down your tank to clean the filter. there are much easier much more effective ways even if you slack on maintenance and allow the filter to plug.
On that same note, if you slack on maintenance any filter will plug up eventually, the UGF just plug up slower than most of the others.

An undergravel filter is designed to be a bio-filter not a mechanical filter and it is exceptional at that task. It uses the substrate as an active bacteria bed to create a huge surface area for bio-filtration. They do serve all too well as a mechanical filter and thus create the need for vaccuming, but then there was already a need for vaccuming as it stood.

UGF's are highly effecient, highly effective inexpensive filters that have been given a poor reputation by people who refused to maintain them and then blamed the filter instead of the fishkeeper. If people treated their cannisters as poorly as they did their UGF's cannister would have a bad reputation as well.

Here is an article that covers the basics and also outlines some very good variations to the basic UGF. It is well worht the time it takes to read it.
http://www.aquasource.org/CMS/modul...ns&file=index&req=viewarticle&artid=17&page=1

Dave

daveedka already said this, but I Have to chime in.
Undergravel filters work by pulling the WATER through the gravel. It is not their job to remove the debris.
The debris ( poop etc.) gets pulled down into the water along with the water and you have to take that out by vaccuuming the gravel.
The whole gravel bed, with the water constantly moving through it, provides a home for bacteria which process ammonia out of the water.
So, with a regular under gravel filter provides great bio filtration. Also since it pulls the debris down, the water stays very clear looking. The debris HAS to be vacuumed out is all.
How does the filter pull water through the gravel? It can use an air pump, to create an upward flow through the riser tube. this is the original way.
OR you can put a powerhead on top of the riser tube and pull the water up the tube that way.

ALSO
somepeople turn the same equipment into a Reverse Flow Undergravel Filter.(RUGF)
This circulates the water through the gravel also, but instead of puling it down through, it pushes the water up through the gravel.
This keeps the poop from collecting in the gravel. Then you use a Hang on Back filter, or something similar, to remove the floating debris from the water.
( thats the "mechanical " filtration)
I ended up with 'gunk' under my filter plate with my first filter( a regular undergravel run by airpump) because I had never even heard of vacuuming thre gravel. I Did have to break it down and start over, but then with vacuuming every week or so, the filter worked well for the rest of the llfe of the tank.( 2 or 3 years) . That was with Goldfish!

the only reason I don't like them is the look of them.

the only reason I don't like them is the look of them.

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That is IMO an acceptaable reason.

Almost every filter format in the hobby has merit, personal preferences are important. I am forbidden by my wife to use anything that has a hose hanging over the back of the tank (due to a siphoning accident some 12 ears ago), so I can't use an external cannister. There are some folks that don't like noise so they don't use HOB's, To each their own.

I ended up with 'gunk' under my filter plate with my first filter( a regular undergravel run by airpump) because I had never even heard of vacuuming thre gravel. I Did have to break it down and start over, but then with vacuuming every week or so, the filter worked well for the rest of the llfe of the tank.( 2 or 3 years) . That was with Goldfish!

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Too little information too late I am sure, but next time insert a 1/4" (or bigger if it fits) airline through the riser tube hole and then vaccum under the plates with that. once the majority of the gunk is out, you can influence flow by making thin spots in the substrate (temporarily of course) this will move the mulm around and allow it to flush out.

In all respects except up front price the Reverse flow set-ups are superior. With my planted tanks, vaccuming isn't a good practice, so reverse flow is a must. Aditionally reverse flow provides a good bit of true mechanical filtration via-the intake sponges on the pwerheads.

This circulates the water through the gravel also, but instead of puling it down through, it pushes the water up through the gravel.
This keeps the poop from collecting in the gravel. Then you use a Hang on Back filter, or something similar, to remove the floating debris from the water.

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Just an FYI, while the mulm does not collect in the substrate with reverse flow like it does in conventional, the munute particles in the water that do get through the prefilters are still caught in the substrate so the end result is much cleaner substrate but you still get the ultra polished look that many people want in their tanks. Hands down nothing polishes water any better than a UGF or an RFUG. Only diatom filters or micron filters compare and they are of course harder to maintain and more expensive.
Dave

daveedka said:

In all respects except up front price the Reverse flow set-ups are superior. With my planted tanks, vaccuming isn't a good practice, so reverse flow is a must. Aditionally reverse flow provides a good bit of true mechanical filtration via-the intake sponges on the pwerheads.

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Don't you just hate repeating yourself so often?

Thanks Dave for hitting all the main points. UG/RFUG are perhaps the most poorly understood filtration technique we use, and are certainly the most poorly maintained. Too many folks feel that out of sight is out of mind, so do no upkeep.

I did many UG/RFUG filters for years, then largely got away from them for a period, but my numbers are going up again (all OE-RFUG), and my tanks are looking (and test) great.