Undergravel Filtration??

sammyday12

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Hi everyone, I was wondering what an undergravel filter does exactly and what i need to do to make it run smoothly? i got my hands on one for free from a friend and have set it up in my 20 gallon tank, but does it need any filter media? how does it work? i’ve got it in the tank & attached the air pump to the tube things and that’s it. sorry if this is ignorant lol but i have no clue how i should manage it at all.
 

MrBryan723

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Read up on the nitrogen cycle if you haven't already started doing that. The info here is pretty simple to understand.
Are there any fish in the tank? You might be doing a fish in cycle if this is a new setup and you have fish.

The air stone in the tube helps pull water up the tube and the water going up the tube is coming down through the gravel where the good bacteria is growing, and into the plate the tube is attached to. For it to work properly the water level needs to be above the top of the tube.
 

JayH

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The undergravel filter basically pulls water down through the gravel. Beneficial bacteria grow on the gravel and provide the filtration. You want a good two inches or more of gravel so there's plenty of surface area.

The bubbles rising in the tube cause water to flow up the tube. That in turn pulls from under the filter plate, which causes the water to be pulled down through the gravel. It's not a huge flow, but the large surface area makes up for it.

Undergravel filters (UGF) have fallen out of favor, but they're still very decent filters. I think a lot of people switched to hang on back (HOB) or canister filters because they provide better mechanical filtration and help keep the water looking cleaner. The UGF is more about the quality of the water from the fish's perspective, not so much the appearance.

One of the biggest problems with the standard UGF is the air stones clog, create irregular bubbles, and physically block the flow of water. If you're not happy with the flow, Google "czech air lift". It's a slightly different approach to the air lift tube that solves these problems. Properly done and supplied with sufficient air they can move massive amounts of water. The only place I know that sells professionally manufactured ones is Swiss Tropicals, but theirs are metric and I don't know if they'd fit in a typical UGF.
 
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sammyday12

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The undergravel filter basically pulls water down through the gravel. Beneficial bacteria grow on the gravel and provide the filtration. You want a good two inches or more of gravel so there's plenty of surface area.

The bubbles rising in the tube cause water to flow up the tube. That in turn pulls from under the filter plate, which causes the water to be pulled down through the gravel. It's not a huge flow, but the large surface area makes up for it.

Undergravel filters (UGF) have fallen out of favor, but they're still very decent filters. I think a lot of people switched to hang on back (HOB) or canister filters because they provide better mechanical filtration and help keep the water looking cleaner. The UGF is more about the quality of the water from the fish's perspective, not so much the appearance.

One of the biggest problems with the standard UGF is the air stones clog, create irregular bubbles, and physically block the flow of water. If you're not happy with the flow, Google "czech air lift". It's a slightly different approach to the air lift tube that solves these problems. Properly done and supplied with sufficient air they can move massive amounts of water. The only place I know that sells professionally manufactured ones is Swiss Tropicals, but theirs are metric and I don't know if they'd fit in a typical UGF.
That was very helpful, thank you so much! I’ll make sure keep an eye one the air stones too.
 

Redshark1

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I still use undergravel filters with my 25 year old Clown Loaches.

My two ug filters are each powered by a powerhead of 1,000 litres per hour output.

15.08.30 Chromobotia macracanthus Clown Loach 6' aquarium Steve Joul (2) - Copy.JPG

Total ammonia is under 0.25 ppm and nitrates are under 40 ppm.

No diseases in the last 25 years.

Why should I change when it clearly works.

Also, my water is pretty clear despite having six massive fish that dig up the substrate all day.
 

Redshark1

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Edit: Picture view now fixed.

Yes sorry I have been having that issue for a while.

It used to work fine.

I don't think there is a way round it.

I've deleted it to avoid frustration.
 

ShipwreckedAquarist

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I use only an undergravel filter and a Nomo. The Nomo added with the UGF is weirdly effective. I change my water once every 18 months. The Nomo stimulates the aerobic bacteria. I can't explain it completely I just know its worked for me. The only thing I have to do is add evaporated water and use a magnet cleaner to clean the glass. Their website is getnomo.com if your curious
 

Beneful1

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When I started keeping fish as a kid back in the early 60's pretty much all you could get were underground filters, box filters or sponge filters, all driven by air pumps. I had an underground filter in my 33 gal tank and it worked very well. I sort of regret that when I set up my new 75 gal last year that I never put one in it as a secondary filtering system along with the canister. Just read up on the Nomo.. seems interesting but I guess I'd have to see it to believe it.
 

tiffani

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I still use undergravel filters with my 25 year old Clown Loaches.

My two ug filters are each powered by a powerhead of 1,000 litres per hour output.

View attachment 632787

Total ammonia is under 0.25 ppm and nitrates are under 40 ppm.

No diseases in the last 25 years.

Why should I change when it clearly works.

Also, my water is pretty clear despite having six massive fish that dig up the substrate all day.
Wow! Nice clown loaches. I’ve never seen them that big before. You take great care of them
 

LeahsTank

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The NOMO sounds suspicious to me. And the person pushing it just joined and only has one post. I suspect that he/she does internet searches for messages containing “under-gravel filters” and joins, then post about its wonders. But that’s just a guess.
 
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