# grivity filter



## bigrift (Aug 30, 2010)

so i was thinking of a way to filter the big tank im makeing and i came up with a idea to use gravity instead of eletric to power the pumps. i dont really know much about this stuff so ill post my idea and if anyone knows any physics then tell me if it will work of not lol. 

ok so my idea was to build a biofilter that hung stright up and down off the back of my tank. a tube would run from the top of the tank (drilled and fitted in the back of the wall) would run straight down threw the filter and then the return would simply be a tube on the bottom going straight into the tank about 2 feet below the inlet. my hope is that gravity will feed the filter and return the water back to the tank without any pumps and sutch but im woundering if the presure of the water in the tank would keep it from flowing back in and instead just filling up the filter and tubes with water and sitting. so a way i thought of to combat this is to have the inlet take in 3x the water the outlet will put back in causeing almost a suction. 

so thats my idea and yeah it may be silly but i really would like some imput on this dont be shy if it wont work tell me lol


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## mozart531 (Sep 25, 2010)

Is this kind of like the design you were thinking of? (The grey box is the biofilter)









I'm afraid this design won't work without some sort of pump. While gravity does pull on the water in the tube, gravity also pulls on the water in the tank. The water in the tube won't move without something pumping it through. If you put an airstone in the bottom you might be able to draw water up from the bottom of the tank (the rising air bubbles pull water up with them). It depends on how big your aquarium is and what your biofilter looks like. The bubble-method usually doesn't generate a lot of flow.


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## SinCrisis (Aug 7, 2008)

If the box is level with the tank it wont pull water regardless of intake size. For gravity to work, the box will need to be lower than the tank. However once the bottom area fills up gravity wont pull it up to the tank so it will site idle. You will need a pump no matter what to move the water.


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## AaronCombs (Feb 26, 2010)

I've tried to pull something like this off as well. Would be great for a power saver. However never worked.


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## SinCrisis (Aug 7, 2008)

Well, a while back i saw an article about creating green energy... where a system used solar power to power a pump that pulled water up to a platform during the day and at night the water is let down via gravity and it runs through turbines to generate even more power. It could be applied to a fishtank if you use gravity to pull-water through a turbine and have the power generated there power the pump to push it back into the tank. That might be beyond anyone's capabilities though...


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## AaronCombs (Feb 26, 2010)

lol actually and sadly that would work. However you'd have find out how much power the pump needs, then how much power the turbine can generate off a 2" or 3" Pvc pipe...

With all that said, you'd also have to compare life of turbine and pump vrs cost of just using electricity over that given time frame. To see which is cheaper. Pending the output of the turbine, which would have to be a mini ... you might be able to setup a battery system (grid) to hold the power. This could also in turn possibly power the rest of the aquarium. 

On another note if you had solar panels and the grid in place, you could be green doing that instead of the turbine.


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## SinCrisis (Aug 7, 2008)

get a bunch of hamsters to run on wheels... jk.


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## AaronCombs (Feb 26, 2010)

lol mice work better.. at least mine did it more than the hamsters.


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## bigrift (Aug 30, 2010)

darn... i figured it wouldnt work but hey it was a good idea lol... it wasnt so much to save energy but just to have something diffrent ya know. i was reading a artical (when and if i get permission to post the link i will) a guy used a bubbler to pump air into his filter and it caused the water inside to push out the the bottom and when the filter was low on water the bubbler shut off alowing a flapper to open at the top of the tank to let more water fill in and it would do this over and over serveal times a minute (i think it said 2 times a min). the air in the filter was released threw a fitting into a hose that went to his stone in the tank to keep it from being just one big rush of air. i guess he figures letting the water sit for about 30 sec in the filter alowed the bacteria to really do its job and keep it free of harmfull stuff.... i dunno sounds like alot to me i probuly wont do it but he dose sell the plans for 25$ on his website. cool idea though and ill post a like if he says its cool to.


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## AaronCombs (Feb 26, 2010)

What he setup is a basic filter... the air causes an internal circulation moving water to filter. I have one on my own tank. Costs about 5 bucks at most to build. Very simple... need a bottle, knife, air line tubing, fork (to make some holes)... then some gravel, filter media, and some active carbon ... and your set. oh and an air pump lol


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## SinCrisis (Aug 7, 2008)

whisper sells filters that are like 11 bucks and it comes with a small pump and it just pushes water up into a chasm and the water flows through a cartridge and comes out as a small stream into the tank. cheap and works.


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## bigrift (Aug 30, 2010)

SinCrisis said:


> whisper sells filters that are like 11 bucks and it comes with a small pump and it just pushes water up into a chasm and the water flows through a cartridge and comes out as a small stream into the tank. cheap and works.


 

tank im building is almost 1k gallons so thats why i was looking to build something not buy it lol


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## Mikaila31 (Dec 18, 2008)

Thing is filters use so little power. Even my monster XP3 canister uses only 28 watts. It would be very simple using any means of electric generation to power a filter, but its really not worth it IMO. Considering what takes up the most energy in a tank, finding a way to passively heat a tank would be much more worth while. The 55gal tank that the filter above is on has a 200 watt heater and being a high tech planted tank with 110 watts of light(compared to 30 watts if it wasn't). If you consider that this is a normal 55 gal. Estimate the heater runs 6 hours out of the day, lights 8 hours, and filter 24/7. That gives you 1200+240+672=2,112 watts per day or 2.112 kWatts. Which based on an power cost average of 11 cents, then it costs 23 cents per day to run. Filter makes up 32%, lights 11%, heater 57%. The heater is the big factor and its hard to estimate how long it is running on any specific tank. The best you can do is see how big a difference there is between the tank and the room. Things like a tightly fitting lid and insulating the tank would have a very noticeable effect. Since glass is very poor insulator. You can do things like fix 1" styrofoam panels to the backs and sides of a tank. Since it gets very cold during winter here I often throw a sleeping bag or comforter over basement tanks at night. However be careful if your lights are on a timer as it could be hazardous for lights (especially high powered lights) to run under a blanket. 

I also thought one day how efficiently could you heat a tank if you pumped water from the tank through a tube in the hood light, then back into the tank? I've never tried such a thing, but by theory especially if you run the tube round and round in the hood it should cool the light while heating the water. The question is if it does it efficiently enough.... It would probably be more theoretical with higher light systems.


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## SinCrisis (Aug 7, 2008)

For heating a tank, i always wondered if one could use a computer. Theres a data center in Europe that uses water cooling and it runs underground to the buildings basement and heats a giant pool of water. This could probably be applied to a fishtank, then you could get the benefits of a cooler computer and not have to heat your tank, but there are far too many downsides such as mobility of the computer, temperature control, etc to deal with.


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