# Pump flow rate



## Okty (Jun 28, 2016)

I'm a newbie to planting aquarium. Going to set up a 84L/22 G (80x30x35 cm) heavily-planted (about 80%), non CO2 & low light (about 0.6 - 0.7 wpl) aquascape. I'm planning to apply Walstad's Natural method. 
I've decided to use DIY external canister for filtration which powered with a submersible pump. 
Now I'm confused about the submersible pump. Some sources say it should be at least 5x of the aquarium volume while others say it should go, at least, 10 times. 
Can anyone help me with this? Thank you in advance.


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## Aquaticz (May 22, 2009)

IMHO the bigger the better especially when it comes to how much media is used. The more the better so long as it does not slow down your filter.



Okty said:


> I'm a newbie to planting aquarium. Going to set up a 84L/22 G (80x30x35 cm) heavily-planted (about 80%), non CO2 & low light (about 0.6 - 0.7 wpl) aquascape. I'm planning to apply Walstad's Natural method.
> I've decided to use DIY external canister for filtration which powered with a submersible pump.
> Now I'm confused about the submersible pump. Some sources say it should be at least 5x of the aquarium volume while others say it should go, at least, 10 times.
> Can anyone help me with this? Thank you in advance.


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## Michael (Jul 20, 2010)

The desired range of flow is usually give as 5x to 10x the tank volume per hour. Some of this, but not all, is directly related to the performance of the filter. Just as important is the circulation in the tank. Ideally, you want a circular pattern of water flow that moves water through every part of the tank.

A sparse, iwagumi design may be just fine with 5x flow rate. A densely planted tank with foliage from substrate to surface often needs 10x. Not all of this needs to go through the filter. You can also use power heads to boost circulation, and this can really help with establishing the circular pattern.

In a Walstad tank, the plants do most of the filtration. So you want the water flow to reach all of them whether it goes through the filter or not.


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## Okty (Jun 28, 2016)

Michael said:


> In a Walstad tank, the plants do most of the filtration. So you want the water flow to reach all of them whether it goes through the filter or not.


So does it mean canister filter in Walstad tank is a bit too much?


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## niko (Jan 28, 2004)

The numbers are numbers but a Michael said - the kind of tank will require different flow rates... So how do you decide what is a good one?

Simple - look at the plant leaves. They must wave gently in the current.

If they do not change the flow pattern of the water. Don't assume you need a faster pump. The flow pattern, if setup right, changes profoundly through moving the outflow wherever needed for your particular tank.

There is a contradiction between the need of flow inside the tank and the flow rate through the filter. The flow through the filter must be very slow. But the flow in the tank must be high enough to move the plant leaves gently. You can't win, but you can find a happy medium by adjusting the flow pattern - by moving the outflow where needed.

Generally it is best to have the outflow shooting along the front glass. There are no obstructions there - decorations of plants. The flow can reach the furthest that way. If the water flow finds a circular pattern something else happens - the water from the rest of the tank gets involved in this movement. It's like stirring soup in a bowl - slow stirring in the middle will eventually make all the soup spin.


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