# One Canister Filter - Two Tanks?



## imcmaster (Jan 30, 2015)

I don't see how you could regulate the inflows/outflows so to keep a constant water level on both tanks? If this went wrong, wouldn't you flood one tank?


----------



## kep (Feb 3, 2015)

imcmaster said:


> I don't see how you could regulate the inflows/outflows so to keep a constant water level on both tanks? If this went wrong, wouldn't you flood one tank?


Good point I hadn't thought of. So maybe if the water level was at the exact same height? Then it wouldn't work out for me. Hmmm


----------



## Diana (Jan 14, 2010)

You are going to have a hard time keeping them emptying and filling at the same rate. 
Are the tanks next to each other, and at the same height? (top of water in the 9g = top of water in the 20g)
If so, connect the 2 tanks with a simple bit of tubing. Ends of the tubing about halfway down (not critical, just below the lowest water change level). Fill this tube with water. 
If you do not want the fish or shrimp going back and forth then cover the ends with some sponge, floss or any sort of mesh too small for the livestock. 

The water will now stay balanced. Even when you do a water change! For example, if you are draining it out of the 20, then the water will flow from the 9 to the 20, so one water change does both tanks. 

Anyway, do the best you can with valves to make them proportional then let gravity fine tune it with this tube.


----------



## imcmaster (Jan 30, 2015)

A canister is a closed loop, so when you have one tank you have 'X' amount of water leaving the tank, and the same 'X' going back into the tank -> constant water level.
But if you have "X" leaving tank 1, and "Y" leaving tank 2, then X+Y goes into the canister, and unless exactly "X" goes back into tank 1 things will go wrong.
Not that you could use a sump, but just to illustrate the difference, a sump would work because of the use of overflows (which keep the water level constant); but a sump is not a closed loop like a canister.

I'd be interested if a DIY expert can get around this problem...


----------



## [email protected] (Feb 22, 2015)

how close are the tanks? could they both dump into a sump?


----------



## kep (Feb 3, 2015)

Hmmm I don't know anything about sumps but I could certainly do some research and see if it would work. I don't know that I would have the space for it. I was planning on putting all of the equipment in the stand for the 9g (black on the right in the pic), but I have a feeling I couldn't make a sump work there. 

Here is the layout. The 9g is at home and I will be moving it to the office on top of the black stand. The 20L is on the left on top of the credenza. You can see the water level on the 9g will be quite a bit higher than the 20. 










Now that I look around, I may have a space on the left of the credenza for another canister. I do plan to have them sharing a CO2 bottle. This is an interesting idea though that I have definitely not ruled out yet. 

Sent from my iPhone using Tapatalk


----------



## me_in_the_box (Dec 24, 2014)

I would put the canister on the 20 and I bet you could get away with just a power head in the 9g unless you have it heavily stocked. It would be a bit risky but if it is established there should be enough bacteria and plants for it to work.

Just don't try to hook up 2 tanks to 1 filter. It will not work out well.


----------



## kep (Feb 3, 2015)

me_in_the_box said:


> I would put the canister on the 20 and I bet you could get away with just a power head in the 9g unless you have it heavily stocked. It would be a bit risky but if it is established there should be enough bacteria and plants for it to work.
> 
> Just don't try to hook up 2 tanks to 1 filter. It will not work out well.


By a power head, do you mean a HOB? For the 9g I'm really trying to keep as much equipment out of the tank is possible. I just bought lily pipes for it and an inline heater. It's not heavily stocked though and I don't plan to. It's been running for about 2 months, so still new.


----------



## theatermusic87 (Jun 22, 2014)

You could probably fit a small tank inside the credenza and se it as a sump, one pmp with some valves to distribute water to the 2 tanks, and then an overflow back to the sump and run the filter off the sump.

If you're into overflow boxes, or drilling tanks you could run the canister on the 20 and then you could run a pump and some tubbng into the 9, with the overflow back into the 20. One canister 2 tanks. Similar to the first idea, only a little less equipment traded for a bit more clutter in your tank, in this case the 20 works as the sump.

Bump: you could probably fit a small tank in the credenza to act as a sump, you'd need a pump in there, your canister filter and then an overflow/drilled hole in each tank.

You could also use the 20 as a sump (only because it's lower) put a pump into it to the 9, then an overflow back to the 20... that way both share the same water and you put the filter on the 20.

You last option and probably the simplest is to put the intake for the canister filter on the 20, the outlet on the 9 and then an overflow from the 9 to the 20. Just be aware with this setup the entire flow goes through both tanks, with no way to slow it down indepently that you get in the prior options


----------



## ikuzo (Jul 11, 2006)

you can try this first, but those 2 tank must be side by side.










that pipe connection must be filled with water first. fill it upside down and quickly turn it inside both tank.


----------



## Diana (Jan 14, 2010)

I have run tanks like ikuzo's picture, except with vinyl tubing, and larger (2") pipe (yup, 
'aquarium hamster tube'). Works great. 
theatermusic has some great ways to make this work when the tanks are not the same height.


----------



## ikuzo (Jul 11, 2006)

hello Diana, how's that even possible?
i thougt running tanks this way make them both have the same water level


----------



## lksdrinker (Feb 12, 2014)

You could use a sort of modified sump system. Run the output of the canister into the 9 gallon, then use an overflow of some sort (hob, or diy pvc maybe) that runs into the 20 gallon tank which would have the input side of the canister pulling water out of that. 

In that scenario the 9 gallon tank would get clean water from the canister. Once the water level is high enough to go into the oveflow, it would "spill" into the 20 gallon tank and that water would be removed via the canister, filtered, and pumped back into the 9 gallon. 

It could work in theory; but seems like a difficult setup when you could just run a small cheapo hob filter or even just a sponge on the 9 gallon or the 20 gallon.


----------



## kilauea91 (Sep 19, 2013)

question for ikuzo and Diana, do you have to periodically prime the tubes or suck out the air bubble in the "water bridge" that may potentially lose syphonage over time?


----------



## AndreyT (Apr 28, 2011)

Are the tanks installed on the same horizontal level? If not, then running a single canister filter for two tanks is out of question. It goes against the very physical principle on which canister filters are based.

If the tanks are on the same level, you can service two tanks with a single canister filter, but you will have to connect them _in series_, not in parallel, as you seem to intend.

The filter intake goes into the first tank, the filter return goes into the second tank. And you need to connect the tanks with a bi-directional siphon tube (an inverted U in the simplest case). As long as the siphon type is fully flooded, the water level in both tanks will be automatically kept exactly the same. Note that in this case the tanks do not have to be side by side. They can be far apart. But as long as the water level is the same and as long as they are connected by a fully flooded tube of any shape, the system will work - the water will automatically redistribute itself between the tanks to keep the water level identical.


----------



## ikuzo (Jul 11, 2006)

kilauea91 said:


> question for ikuzo and Diana, do you have to periodically prime the tubes or suck out the air bubble in the "water bridge" that may potentially lose syphonage over time?


no, as long as both input and output of the tube stay below water level it will be just fine. weekly maintenance is recommended though, to avoid accidents because sometimes air bubbles can enter and trapped inside the tube reducing water flow.

to fill and flip the tube will just take a few seconds anyway.


----------



## caique (Mar 16, 2012)

Just get yourself another canister and make it simple. I have a Eheim 2026 on my 25 but it would probably be to much for a 20 on my 20 long I use a Eheim G65 with a 60 gallon sponge filter. It is a bit overfiltered:hihi:


----------



## scapegoat (Jun 3, 2010)

you're going to spend as much jury rigging this and repairing damage when it floods as you would on a second filter.


----------



## kep (Feb 3, 2015)

Yeah this all sounds like too much. I'm just going to get another canister and buy extra long hose so I can hide it somewhere. 


Sent from my iPhone using Tapatalk


----------

