# Canister Filter for Multiple Tanks



## longbowaj (Nov 25, 2007)

I currently have a 20H light/medium planted tank. I need to do some upgrading on it, new lights and substrate, so i can put in more demanding plants.

Since I've been thinking about doing this upgrade I've also started thinking about having a second tank, probably a 20L. I really want a tank for shrimp but know that a lot of fish will eat the shrimp so I think i would have a shrimp tank and a fish tank.

To try and make things easier I am wondering if i can use a single canister filter for both tanks. I am a little worried about how far apart I can put the tanks without reducing the flow too much. The idea I have is to put a tank on either side of my TV. I would probably build the stands/entertainment center myself. As a rough guess I would think the tanks would be 5ft-6ft apart. With the filter in the middle somewhere.

To make life easier when doing the plumbing would it also be possible to have third line for water changes. Open third outflow, turn off tank outflows to empty the water then do the same on the inflow to fill the tanks.

I have never used a canister filter before so any help would be great.


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## hoppycalif (Apr 7, 2005)

A canister filter works only because the water siphoned out of the tank to the filter is returned back to the tank - there is no net gain or loss of water in the tank. This doesn't work as soon as you put two tanks on one filter. Neither the inlet flow to the filter from each tank, nor the outlet from from the filter back to each tank is limited so as to maintain the no net gain or loss in each tank. A worst case would be losing the siphon from one tank, and having the outlet to the other tank be heavily restricted by plant debris. That would let the canister filter dump most of the water from one tank into the other.

You can't solve this problem with control valves either, because conditions at the inlets and outlets in the tanks changes, requiring constant adjustments of those valves.

Just bite the bullet and buy two smaller filters, one per tank.


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## Bert H (Mar 2, 2004)

What Hoppy said. I can't envision any way you could make work what you propose.


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## longbowaj (Nov 25, 2007)

Is there a particular filter you would recommend?

Would just using a sponge filter be enough for this size tank. I just don't like the way HOBs look and it seems that with planted tanks you need less filtration and the surface agitation from a HOB hurts the CO2 levels.


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## Logan's Daddy (May 3, 2008)

How about a HOB / canister like mine... A Marineland HOT Magnum? Best of both worlds and a ton of flow (250 gph!)


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