# UnderGravel Filter



## Dgjimbob (Jan 11, 2006)

I have an undergravel filter for my one ten gallon. My question is do they need any cotten in them. How exactly do they work.


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## emc7 (Jul 23, 2005)

Some people put a layer of floss under the gravel on top of the plate. It should make a better filter, but it makes gravel washing too hard, so I skip it. The other place you could put cotton is in a cartridge on the upright tube, but ususally that just has carbon An undergravel just needs a plastic plate under the gravel, an upright tube stuck in a hole in the plate, and something to move the water, usually an airstone or powerhead. You suck water up the tube and that pulls water down through the gravel. Fish poop, dust, etc. is sucked down into the gravel. The gravel provides a surface for the bacteria that eat ammonia and nitrite to live on. Like a sponge, it biological only, it does not remove any debris from the tank, you need to gravel wash with a siphon or power filter to do that. And also like a sponge, it can get really gross if you don't keep up with the maintainence.


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## rcomeau (Apr 23, 2006)

I never heard of using cotton for any filter. I suppose you are referring to the cotton-like material that is in some filters. If so, it is most likely polyester fiber. The kind that is also used as stuffing that you can get from a craft store in large bags for about $1. Such fiber is inert with the purpose of providing a place for good bacteria to grow on. The job of the biological filter is to move water past the good bacteria. Two types of good bacteria provide "filtration" to detoxify the water... ammonia -bacteria #1-> nitrite -bacteria #2-> nitrate

For an under gravel filter, the gravel is the inert material that the bacteria grows on. Bubbles moving up the tubes cause the water to flow across the bacteria on the gravel.

Here is a website that has a good summary... http://www.bestfish.com/ug.html

I had a 10 gallon tank and used the simple in-tank corner filter. The middle of the tank was bare bottom with gravel on just the sides. That way the corner filter provided the biological filtration and the bare bottom and gravel was easy to vacuum. 

I'm no expert but I looked into UGFs enough to form an opinion that it is an old and simple filtration method. It seems to have lost popularity perhaps because more money can be made selling us more complicated filters or because they really are hard to vacuum clean. They say it eventually clogs too much and/or gets so dirty that you have a bacteria problem. 

I'm trying an UGF myself for the first time since the beginning of April because it is a 50 gallon tank, I like the look of natural gravel across the entire bottom, and I don't like the look and noice of other filters. I'm using relatively large gravel stones (I screened out the smaller stones) with hopes that the large stones will be easy to vacuum and because larger stone won't contribute to the clogging problem. It seemed like a good idea but I'm already considering pulling out the UGFs and using two corner filters with a bare bottom center again. Breeders keep bare bottom tanks for a reason. They keep water moving across good biological filtration, keep air in the water by aggitating the surface, and vacuum clean the rest as easy as possible.


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## emc7 (Jul 23, 2005)

I like to keep thick gravel in my Malawi tanks, the mbuna spend time moving it around rather that chasing each other. I think thick gravel with no flow can lead to anaerobic patches, so if I have gravel in a tank, I have an undergravel filter. Bare patches of exposed plate reduce the effectiveness of the UG filter, but since its not my only filter, I don't mind, I just fill them in and let the fish start over. You do have to gravel wash or you get enough decaying stuff in the gravel that the water changes can't get the nitrate down. I tried filter floss with a UG once, it was enough, never again. With power heads UGs are quiet and effective. I use sponge or box filters in bare tanks to breed angels and other substrate spawners, but I've heard of jewels digging down to the UG and laying their eggs on it.


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## Dgjimbob (Jan 11, 2006)

How do u maintain a UGF? When you say syphon the gravel do you mean vacuum it? If so, how often should it be done? Do you have to clean underneath the filter? Please help if you can.


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## emc7 (Jul 23, 2005)

When u change water, use a fat tube and vacuum the gravel (u don't have to do the whole tank at once, just move around the area u do). u cant' get under the plate without taking the gravel out of the tank, so i only do this when i need to break the tank down for another reason (like moving it), but you can stick a hose down the upright tube and get some of the crud under the plate out.


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## xerxeswasachump (Mar 29, 2006)

Why is it so important to syphon out the gravel of a tank? 
Wouldn't plants eat all of those gross things in the gravel? What exactly are anerobic pockets? Why are they so bad? 

Also, is there anything i can do for my 55 gallon tank with 3" of gravel/flourite already in? I don't have a long enough syphon tube to actually get to the gravel. I usually just do water changes by the bucket, the syphon takes 20 mins just to fill 1 bucket, so i have taken to just using the bucket to remove water.
Am i doing anything very wrong? I really want to do as little maintenance as possible, that is why i have plants and why i am about to get some power compact lighting. I really don't mind algae either, anything that eats crap and means i don't have to ruin my aquascaping and freak out my fish is ok by me.

EDIT: if i am being completely retarded feel free to call me out on it.


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## joe kool (Jan 24, 2005)

emc7 said:


> I like to keep thick gravel in my Malawi tanks, the mbuna spend time moving it around rather that chasing each other. I think thick gravel with no flow can lead to anaerobic patches, so if I have gravel in a tank, I have an undergravel filter. Bare patches of exposed plate reduce the effectiveness of the UG filter, but since its not my only filter, I don't mind, I just fill them in and let the fish start over. You do have to gravel wash or you get enough decaying stuff in the gravel that the water changes can't get the nitrate down. I tried filter floss with a UG once, it was enough, never again. With power heads UGs are quiet and effective. I use sponge or box filters in bare tanks to breed angels and other substrate spawners, but I've heard of jewels digging down to the UG and laying their eggs on it.



having any exposed patched will cause the anerobic patcher to develop much faster as there will be little to no water movign in the much thicker areas. 

I myself have gone totally away from UG filtration becouse of keeping cichlids and the dead pocket syndrome. If I have to vaccume out the gravel anyway might as well have it to where I can make it as thick or thin in areas as I wont without having to worry about causing more problems. I've also started using sand in many of my aquariums and have come to the conclusion that I'll never set up another aquarium W/O sand again. It has many benifets and is just as easy to maintain as gravel if vaccumed and flushed properly just like you have to with the gravel (you pinch the hose when using the vaccume in the sand to keep from sucking it out of the tank and it works great or get the python systems that have a flow control knob ... even better) 
"My" fish are much happier on the sand as it's closer to natural for them and they frolic and dig in it continuiously. I enjoy going home after work just to see how they've decorated today  you absoultely don't want to use sand with the UG filter. The finer the gravel you use the less effective the UG becomes. 

The only way I would use an UG filter today would be with Reverse flow power heads and a over flow going to a sump which would effectively blow the "poop" and crap out of the gravel and into the water and "ideally" be sucked in by the over flow system into the sump. BUT being as I'm sticking to sand for the enjoyment and heath of my fish ... that's not an option


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## emc7 (Jul 23, 2005)

The reason you siphon out the crap is to keep the nitrates from soaring, If you have a lot of plants to eat the nitrates, I guess leaving the crap is ok. I never hear plant people talk about gravel washing tanks.


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## emc7 (Jul 23, 2005)

joe, how do you keep the sand from getting in the canister filter and wrecking the impeller.


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## joe kool (Jan 24, 2005)

emc7 said:


> joe, how do you keep the sand from getting in the canister filter and wrecking the impeller.


I use Fluvals and their impeller is in the lid magnet up, "upside down" compaired to the magnum 350 or the like, so the sand if it gets in the canister (I've raised the intake considerable compaired to the 1" off the botton like normal ... mines about 5-6"), which it does espicially around spawning time, stays in the bottom of the canister in the "foam" first stage of filtration. Been running like this for 2+ years so far and no hickups. I even have the Hydor "in-line" heater on that tank and no issues with any sand going through it either but the heater is on the return-to-tank side of the filter  

my 100gal is a sump over flow style with a mag 350 for mechanical/polishing. But that mag 350 pumps out of the sump instead of the main tank and into the main tank. So there's no chance of getting sand in it unless somebody freaks out and goes crazy with sand LOL. 

My 46 BF has sand with a Aquaclear 500/110 but the intake is only about 10" or so down in the tank on a 30" tall tank ... I think ... close to 30" n e ways. And I've only found sand in it once and it cleaned right up.


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## emc7 (Jul 23, 2005)

Thanks, I'd like to try a sand tank someday.


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