# Undergravel filters?



## Fishy:) (Apr 10, 2010)

I dont get these filters. I know you put them under the gravel/substrate and all but what if you want to change the filter? do you have to take all the gravel off, lift it up, put the new filter in, and then put it back under the gravel?that would be ridiculous. atleast to me. well just wondering


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## bmlbytes (Aug 1, 2009)

In this case the filter media is the gravel. You use a gravel vac to clean it out. The water is sucked down through the gravel, into an empty space under the gravel and up a tube to the top of the tank. All the gunk gets stuck in the gravel. You vacuum the gravel out with the gravel vac on the siphon or with an electric gravel vac. The UGF should state how much gravel you should put on top of it, usually 2 to 3 inches.


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## bmlbytes (Aug 1, 2009)




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## Fishy:) (Apr 10, 2010)

COOL!! thanks guys! is this better than the regular filters?


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## bmlbytes (Aug 1, 2009)

Not usually, but they are nice to have for small tanks or as an accessory filter.


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## Guest (Apr 28, 2010)

lol you dont need to install a medium. a UGF comes with plates. the gap between the plate and the subrate is where your gunk gets collected. there is nothin to 'replace' though every 6 months or so you will need to take down your tank completly and clean the bottom.


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## Mikaila31 (Nov 29, 2009)

the main issue with UGF is muck builds up between the plate and the bottom glass of the tank. This can lead to issues if you don't remove it occasionally. Something I have seen a few people do recently is reverse the flow on a UGF, its call simply a reverse UGF. Its pretty straighforward, you just pump water down the pipes and up through the gravel, it is suppose to fuction much better this way. You can google it and find lots of different plans on how to set them up for reverse flow.


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## Fishy:) (Apr 10, 2010)

oh well i think ill stick with the regular filters lol


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## pinetree (Nov 29, 2009)

Twenty years ago I had them in most of my tanks as HOB and canister filters were very expensive back then. I liked my UG filters and never, ever disassembled the tanks to clean it. In fact, I never cleaned under the plate, I just vacuumed the gravel regularly and my tanks were very clean and tip top. When I finally did break tanks down to downsize my fish keeping in general, there was no gunk under the filter plates. I think they worked very well, although I imagine modern filters work better and have more surface area for bacteria to grow.


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## emc7 (Jul 23, 2005)

I doubt any filter can beat UG for shear amount of surface area. Every side of every gravel piece is potential bacteria surface. The trick is getting enough and even enough flow. I always had to break my UG tanks down and clean under the plates to get the gunk out. So I do think modern filters are less work.


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## TheOldSalt (Jan 28, 2005)

UGF's don't get along well with live plants, and they create a LOT of nitrate. As such, you'll have to make regular water changes without fail. On the other hand, they can't be beat for simplicity and stability.
If you get too much gunk under them, you're feeding your fish too much.
I like to use them in conjunction with some other filters.


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## Brontegirl (May 10, 2010)

I use an UGF with a powerhead in addition to my filter. If my filer fails, I figure at least I have a backup. My plants are growing like crazy. The UGF doesn't seem to affect them.


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