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Hi Mike,

I have made one and used it on a fry tank. The tank was a over sized 2 footer, and the filtration was great. I had about 20 Rainbow cichlids and about 10 Jack dempseys in the tank and never had any problems with the water. Although, it is effective at purifying the water, it doesnt do much for cleaning up waste. You will need to siphon the gravel more often than usual than if you were to use a more powerful sucking filter system.

So, in effect, it is a great water purifying filter, but not very effective for minimising waste matter.



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I used sponge, porous glass (the green rocks...unsure of name) and pebbles. And this was still only effective for purifying the water.

I think it all comes down to how powerful the air pump is as to how much waste it actually draws in. Because the tub i used for the filter area was approx. 3 inches higher than the gravel bed, any waste that fell below the top level of the filter would settle on the gravel and have to be removed by syphoning.

I dont think there would be anyway you could make it powerful enough to actually draw waste in from below the filter line.

I think it might need to be stipulated in the DIY article that this type of filter is only effective as a water purifying filter and not a waste removing one.

Hope this helps you a bit more.

Cheers, Alan.

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Hi Guys,

The coke bottle idea is ok but I found it to be a real task cleaning out the filter (time consuming).

Woman's stockings are great to fill up with carbon as you can place them around the top of the filter and it will polish the water up nicely. Remember to run the water through the stocking filled with carbon to remove the fine powder before placing into your tank.

I had ceramic noodles around the coke bottle then argyte crushed marble then filter wool on top. You could place a pipe into the top of the bottle for greater suction.

I used these filters in my 4 - 5 -6 foot tanks with great effect.

All my tanks had coke bottle filters in them but I have changed my design to a better filter system now.


Brett woot.gif

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Hi Mike

That filter is designed to do biological filtration only, you basically need 2 types of filtration, the other is mechanical.

Mechanical filtration is designed to remove the larger particulate matter from your tank and the Biological filter is there to deal with the removal of chemical build up.

Mechanical filtration is done with a high flow rate and biological is done with a slow flow rate.

That filter is designed to have the water flow over the gravel at a rate that allows the bacteria to do its work, this is to facilitate dwell time. This filter deals with what is called the Nitrogen Cycle. The gravel houses bacteria.

As waste products break down they are converted to ammonia which is toxic to fish. Niotrsoman bacteria in the filter break that down to Nitrate which is again broken down by another bacteria called Nitrobacter, this bacteria converts the Nitrate to Nitrite which is not toxic. Nitrite in your tank can be see as a yellowing of the water and is the reason we do water changes.

You can change this filter design to make it a mechanical filter by changing the flow rate by adding a powerhead in place of the air lift.

Another great plus with this filter is that you can move it to a new tank and provide an immediate bacterial colony that will prevent what is known as “New Tank Syndrome”

Please excuse the spelling mistakes. I will fix them when I get back from the committee meeting.

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I used two of them, in a 3" tank while I was building a trickle filter. They worked fine but they don't look very nice.

I found cleaning no problem as I only cleaned one at a time.

I also found that their mechanical filtration was OK even if they are not ideal for the purpose.

I have kept them in case I need some additional filtration in a hurry.

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I knocked one up for a 3ft for an emergency, and being lazy, I left it in there, and it works great for biological filtration.

I use an Ice-cream tub for biological, and an Internal power filter for mechanical. Works fine.

One thing I noticed is that my Bristlenose love to get into the coke bottle compartment through the lid !

They brave the bubbles and dart in, and I can often see them through the bit of coke bottle sticking up above the media.

So these filters double as Bristlenose homes laugh.gif

If you wanted to, you could use a different vessel for the media, rather than an ice-cream tub, and make it look a bit better. Or just camouflage it.


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They are effective.

Easiest way to clean is...

tip the whole lot into a bucket of water you've removed from your tank.

Stir. remove gravel - throw away rubbish.... then re-assemble.


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G'day Mike

I use lots of these filters. Each one of my two foot tanks has one of these filters. They are great. thumb.gif

The media I use is just gravel. I tried lots of other stuff including filter wool, but it is too laborious and time consuming to clean.

To clean these wonderful filters all you need do is put the gravel syphon into the gravel.

Oh yes and if you think they are just a biological filter think again, you should see how much "gunk" comes out of them when I gravel syphon.

I also use the extension tubes (OR lift tubes) on my filters.

cya Matthew...

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