# Undergravel Filters how do they work?



## NMrayn (Dec 11, 2008)

Hello again in fishly land lol,

Like i said before i am getting back into tanks and i have never used an undergravel filters, are they better the the ones that sit on the tank? i have guppies and i ahve found 2 of them stuck to the filter i had, and i would like to keep them away from it. Is undergravel the way to go? Or is there something i can do with the filter i ahve now? THANKS FOR THE HELP :-D:-D:-D:lol::lol::lol:


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## flight50 (Sep 30, 2008)

they work. use them on larger substrate though. if you have a planted tank, UGFs are not your friend. i don't care much for them and others will probably say the same. they also take up a little more room and takes away depth from the tank. as far as a fix. one thing i did, was just take a sponge. dense if you can. and create a filter around your filter intake. your sponge will clog but in turn will keep your HOB filter cleaner since your keeping most debris out. it also gives the bacteria an extra place to grow. when it clogs, just rinse in old tank water. don't use tap. it has chlorine it it.


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## Mikaila31 (Dec 18, 2008)

Undergravel filters are really old outdated filters, designed long ago. They work fine at first, but eventually they cause water quality issues as more and more stuff gets stuck under those trays.

As for the filter you are using, what kind is it? Fish should not get stuck to a filter. This is normally a bad sign that something is wrong, not with your filter, but with you water or fish. Do you know what your water stats are in terms of ammonia, nitrite, and nitrate? And how long has the tank been up?


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## NMrayn (Dec 11, 2008)

Mikaila31 said:


> Undergravel filters are really old outdated filters, designed long ago. They work fine at first, but eventually they cause water quality issues as more and more stuff gets stuck under those trays.
> 
> As for the filter you are using, what kind is it? Fish should not get stuck to a filter. This is normally a bad sign that something is wrong, not with your filter, but with you water or fish. Do you know what your water stats are in terms of ammonia, nitrite, and nitrate? And how long has the tank been up?



Thanks for the help and i miss typed LOL i had a guppy give birth and i saw one get sucked up into the filter LOL again THANKS for the help,


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## SinCrisis (Aug 7, 2008)

ive seen a neon tetra get too curious and get stuck on the intake of my filter... I jsut turned it off and it swam away. Sometimes, if your filter is too powerful it can happen. Also the sponge concept is usually used more commonly in fry tanks which, in ur guppy's case, woulda been a good idea


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## Tyyrlym (Jun 1, 2008)

There's nothing intrinsically wrong with an UGF, it will biologically and mechanically filter your water and so long as you keep up the maintenance you'll be fine. The problem is that the maintenance on them is a bear. Since the plenum (the space under the plates) is large and the flow not that high any junk that makes it through the gravel will tend to settle out in the plenum. Gunk can also build up on the plates themselves. If you don't clean the plates both over and under on a regular basis the gunk will build up, nitrates will start to take off, and it just gets ugly. Cleaning the plates obviously entails pretty much tearing your tank down completely in order to get at them and under them. The aquarium I kept when I was little and with my parents had an UGF. The tank was only about 20 gallons but it convinced me to NEVER use one.

TLDR version, they work just fine but cleaning is a pain. Get a hang on back like a Penguin or an Emperor.


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## WisFish (Dec 16, 2008)

My 55gal tank has used an UGF for the last 18 years without the tank being taken apart. You just have to clean the gravel with a gravel vac. With the type of stand I have I can see what's under the plates. The vac will get some of garbage but not all. But I've never had a problem with water condition issues.
But my take on filtration is get the type that you feel most comfortable with maintaining. Because for ANY filter to work, you have to understand the correct way to maintain it.


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## jpd1107 (Dec 20, 2008)

Have you tried a reverse flow undgergravel filtration? it works well w/ my 3 tanks


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## Oldman47 (Sep 7, 2007)

If you have a fully cycled filter that is working on your tank, I would not change it. To prevent fish being sucked up by the filter you can place a sponge filter over the intake. Just cut a slit in the center of the filter sponge and slip the inlet tube down into it. It keeps fry from being sucked up and gives an extra layer of biological filtration.
Filter sponge laying on my desk top








Sponge in place on filter tube








The extra sponge is easy to clean using the gravel vac during a water change. Things stick to the outside but otherwise it stays pretty clean by itself.


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