# Hows this? DIY filter



## JasonPolen (Dec 26, 2013)

I know this has been done before, but I have no idea how to calculate flow rate and nitrite/nitrate removing bacterial capacity. If you read my post in the _introductions_ section, you'll remember the under filtered 55 I'm not supposed to touch. Well I set this in there and wanted to get some input. 
The tube is a 1in OD acrylic lift tube. 
1) ~1in sections of straw as the base, allowing air through and helping keep the rising air even to distribute growth.
2) dollar store nylon sponge
3) gravel, half stays submerged as bubbles pass through, the other half is almost always in air; however, large bubbles rise and pop over these so they are always wet.
4) filter floss
:? any real water going through? or should I take some sponge out to increase flow, I thought maybe the gravel and its unique interaction with the air would result in different bacterial growth.
_*I would love if someone could shove this into the DIY forum*_, started typing in the wrong tab again, whoops. First day on the forum gonna be posting everywhere!


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## lohachata (Jan 27, 2006)

if there is no water flowing up out of the tube then the flow rate of your filter is "0"...
all you are doing is pushing air through the water...cut the tube back until it is below the waterline...


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## JasonPolen (Dec 26, 2013)

lohachata said:


> if there is no water flowing up out of the tube then the flow rate of your filter is "0"...
> all you are doing is pushing air through the water...cut the tube back until it is below the waterline...


it is below the water line, the gravel is half submerged because air has built up internally,in the chamber containing the gravel, did you see the video?


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## JasonPolen (Dec 26, 2013)

well design has been changed, settled on ust filter floss, not gonna worry about gravel


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## BettaGuy (May 6, 2012)

to test if any water at all goes through raise the pipe a tiny bit above the water to see if any water comes out the top, that's what I do with my sponge filters


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## lohachata (Jan 27, 2006)

here is the problem...the air input appears to be below the filter media...it should be above it..that way the bubbles will pull water through the media without obstructing the flow through it...also make sure that the top of the lift tube is a couple of inches below the waterline so there is good surface disturbance..using an airstone will also enhance water flow and aeration..

sorry , i didn't notice the link when i first responded...


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## JasonPolen (Dec 26, 2013)

lohachata said:


> here is the problem...the air input appears to be below the filter media...it should be above it..that way the bubbles will pull water through the media without obstructing the flow through it...also make sure that the top of the lift tube is a couple of inches below the waterline so there is good surface disturbance..using an airstone will also enhance water flow and aeration..
> 
> sorry , i didn't notice the link when i first responded...


Well I've seen filters for sale in the eu that worked like this, one of the problems of filters that are heavy in foam often block all flow when the foam is not open cell. so you have a bubbler and no filtration. That is why it is important to use clear tubing to check for bacterial growth and the behavior of the bubbles. i learned that my design allowed bubbles through, but not water. so there was no true flow. i have since decided to use glass fragments and lava rock to allow aerobic an anaerobic bacterial growth within the filter, another reason I opted for the lower inlet for bubbles. I used ridged tubing for the air inlet to help the filter look better(hard to connect air stone to this), and the body of the filter would recombine and small bubbles anyways, so an air stone is useless; however, air stones would increase flow, gas absorption, surface disturbance, and overall well being of an under-gravel filter or something of that sort.


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