# How long filter intake should be ?



## ppaskova (Apr 27, 2010)

Hi Guys

Just started cycling my new 29Gl tank with AC50 filter. But when I started it i realized that filter intake not even long enough to reach half of the height of the fish tank. Does the filter intake should be long and should be almost to the bottom of the fish tank or it is relay does not matter as long as it is in the water ?


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## solarz (Aug 31, 2010)

Nope, it makes no difference. The purpose of a filter is to pass water over the media and to create water movement. The length of the intake makes no difference as long as it's in the water.


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## BillD (Jun 5, 2006)

There is a reason to have it near the bottom and that is to improve water flow and remove debris that has sunk. There should have been an extension piece with the filter, or you can buy one to add.


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## bob123 (Dec 31, 2009)

I agree the tube should be within an inch or two from the gravel to improve water circulation.


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## RevoBuda (Sep 3, 2011)

i have always had 2 filters on my larger tanks. Usually i keep one suction mid way in the tank and the other much further down. It does move the water around and will assist in having crap filter into the physical media of the filter. Always try to have the water move around in your tank to avoid pockets of sludge forming.


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## solarz (Aug 31, 2010)

In a planted tank, sunken debris creates mulm and improves plant growth.


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## ppaskova (Apr 27, 2010)

So, Now I'm confused. It will be a planted tank. Should I put an extension for it to be close to the ground or no ? Also would the extension restrict some flow ?


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## ThaChingster (Feb 25, 2011)

ppaskova said:


> So, Now I'm confused. It will be a planted tank. Should I put an extension for it to be close to the ground or no ? Also would the extension restrict some flow ?


Doesn't matter - depends on personal choice of aesthetics

and no, it will only restrict flow if plant matter gets stuck on intake strainer


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## ppaskova (Apr 27, 2010)

ThaChingster said:


> Doesn't matter - depends on personal choice of aesthetics
> 
> and no, it will only restrict flow if plant matter gets stuck on intake strainer


OK. But my question is the filter circulate all the water in the tank if I'll not extend it ?


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## ThaChingster (Feb 25, 2011)

ppaskova said:


> OK. But my question is the filter circulate all the water in the tank if I'll not extend it ?


yes it will circulate all of the water, but the flow of water may be decreased in some areas


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## ppaskova (Apr 27, 2010)

ThaChingster said:


> yes it will circulate all of the water, but the flow of water may be decreased in some areas


So I'm guessing it's better to use the extension, for better flow circulation ?


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## Lee_D (Jun 11, 2010)

I don't think the extension will have any significant effect on circulation at all. I think it is included to take into account the effect of Gravity. The water in the top half of the tank will tend to have less particulate in it than the bottom half of the tank. Thus the tank will be cleaner if you remove the water from the bottom half of the tank and put it back at the top.

My intakes tend to be about two thirds of the way down to the bottom, but above the leaf line.

Lee


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## BillD (Jun 5, 2006)

Since an AC filter expells water along the surface, it stands to reason that the farther from the surface the intake, the better the flow will be.


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## solarz (Aug 31, 2010)

BillD said:


> Since an AC filter expells water along the surface, it stands to reason that the farther from the surface the intake, the better the flow will be.


Take a bucket of water, stir it with a stick. Vary the depth of the stick when you're stirring the water. You'll notice that it really doesn't matter whether you're stirring near the surface or at the bottom, the entire bucket of water will eventually be flowing at the same rate.


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## BillD (Jun 5, 2006)

That may work,eventually, in a pail, but an aquarium isn't round. I know from experience with a swimming pool, which uses a much more powerful (relatively) pump that the flow is not equal everywhere. There are always dead spots.


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## absun (Aug 28, 2011)

Irregardless of the flow of the tank, IMO water, like all other volatile substances on this planet, will tend to take the shortest route with the least resistance, which is the distance between the intake and outflow... So the longer the distance, the better the circulation and filtration


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## HOWsMom (Jan 3, 2012)

Personally, I prefer to have my intake as far away from my output as I can manage.

I think Bill is spot on - having two fairly separated areas of high flow will help to circulate the water better.

*A recent example from personal experience :*

Take a 30g tank with HOB filter rated up to 40g. 
Add in a fairly major cyanobacteria outbreak (on one hand - the blue-green blanket looked kind of cool from my 9-yr old son's point of view. Not so much from mine).
Take daily major water changes.
Take out all decorations and bleach them (then soak them in a bucket with a significant amount of Prime to dechlorinate them).
And still can't get rid of the cyano.

Cyanobacteria thrive in water that is fairly still.

Add in a Fluval U3 internal filter (keeping the other filter going still).

Within 24 hours, the cyano was GONE.

What finally fixed it ? Increased water circulation. I had to get that water moving more than it was.


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## mkblitz (Oct 12, 2011)

just use your common sense, and experiment. I run mine 5 inches from the bottom. it also depends on the dimensions of your tank and the adjacent surface your filter is pointing. It does matter


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## kuopan (Sep 6, 2010)

agree, that it really makes no difference...

I Would only recommend to let the intake sit higher if you have sand as substrate so it doesn't destroy your impeller.


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