# Can I get away with One New Canister Filter?



## greenman (Nov 4, 2006)

So here's the deal. I currently have a 29 gallon moderately planted tank with Co2 and a power filter. I want to move to a canister filter. I have two things to keep in mind and I'm not sure they can be solved together. First, I need something quiet, really quiet. Second, although I currently have a 29 gallon tank, I plan on upgrading to a 90 or 100 gallon in 1 year. I'd like to be able to get one filter that could be turned down to accommodate my current 29 gal tank, yet could eventually handle the larger tank down the road. Am I asking too much?


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## Squawkbert (Jan 3, 2007)

Yes, you're asking too much (IMHO).

Really quiet=Eheim. A 2215 would be a little overkill for a 29, but doable and it would, when added to a 2217 (or slightly larger filter) later on, be a good match for a large tank.


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## redstrat (Apr 3, 2006)

The filstar XP3 would be adequate for your future plans and it should work for your 29 too if you use the included flow control valve to turn it down some. It may be ok at full blast but I wouldn't count on it, at least it has the valve


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## greenman (Nov 4, 2006)

Thanks for your HO Squawkbert. 

How difficult is it to add a second canister once I get the new tank? Is it going to be a plumbing nightmare? I hadn't thought about doing something in tandem.

What do you think about davis.1841’s idea of an XP3 and turning down the flow control valve?


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## Linda (Mar 3, 2006)

i agree that the rena filstar xp3 would work for you, i have an xp2 on my 29gal and it does a good job i also have an xp3 on my 90gal mbuna tank. these filters are fantastic as you have lots of options for how they are set up. really good filters i find and easy to maintain.


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## JERP (Feb 4, 2003)

Using a valve to turn down the filter may make the filter noisier.

You can also run at full speed but add larger or multiple inputs and outputs. That way you are moving massive amounts of water, but slowly so you don't destroy the tank.


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## tefsom85 (Jan 27, 2007)

Some of the Eheims (eg. professional series) have flow control valves on them. This may be an option. One thing I don't know is whether or not impedeing the flow has an affect on the pump's lifespan. Typically filters are meant to deal with some backpressure but its still something to look into. I'm sure others here will chime in.

For my 120G, I currently have a 2213 driving a reactor and a 2028 for the main filtering job. The 2213 has been a workhorse - 16 years and still going. The 2028 is only a couple years old, but so far I love it. For my tank, I like having the two filters... however, the downside is having 2X the filter hardware in the tank.

Just my $.02


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## Muirner (Jan 9, 2007)

I have an XP3 on my 55 gallon. It's very quiet, the only time it made noise is when I didnt have something under it and it was sending vibrations through the metal stand. I even have it turned back some right now because I just moved some stuff in my tank and want it to take hold prior to blasting it. 

Setting it up is easy, and fast.


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## AMP (Nov 11, 2006)

I second Squawkbert, The Eheim 2215 Is super quiet, you can always put a Ball valve in line on the discharge side and cut the flow back, but don't decrease the input side. I have the 2215 on my 55 along with a Flival 404 and 2211, the 2211 handles my UV the other two are Bio and Mech filters.

My 90 I have invested in the 2028 Pro3e and will transfer the 2215 to it as well, Plumbing the eheim is no big deal Unless you want to be like me and hard pipe it in  By the way the new 20 series are full flow programmable, I am curious , actually anxious to try this out


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## Blacksunshine (Aug 11, 2006)

Pro IIIe. Electronic flow control. maybe at its lowest setting it would work well for a 29 gal. 
But they are about $350. tho you would have the most kick ass cannister on the planet.


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## BryceM (Nov 6, 2005)

I'd reccomend an Eheim 2217. They're an older design, but are fairly inexpensive and absolutely bullet-proof. I use a pair of these on my 180g tank. They're so quiet that it's hard to belive there are actually moving parts inside. This should be large enough for a 90g tank if it isn't heavily stocked. For the 29g tank just partially close the valve on the output side. From a fluid dynamics and engineering point of view there is no downside to this apart from wasting a bit of electricity. It shouldn't result in any extra noise either.


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## Squawkbert (Jan 3, 2007)

I would actually be inclined to advise against limiting the output w/ a ball valve on a 2215 or 2217 - my 2215 actually operates under slightly negative pressure - impeding output could change that and result in a leak if you have a marginal o-ring, whereas it wouldn't leak if left alone. If you have too much flow, some combination of drilling out the spraybar holes and putting a sponge or two in the inlet side should fix it.

if a (Pro IIIe. Electronic flow control. maybe at its lowest setting) would work, it may be a better way to go, as long as you don't mind keeping all eggs in one basket.

If you go w/ multiple canisters down the road, just plumb each independently. You can stack/stagger spray bars on one side and have 2 different intake heights on the other side. Anything that doesn't result in spraybars pointed right at intakes, and allows adequate circulation w/ few/no dead spots will work fine.


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## BryceM (Nov 6, 2005)

Restricting the inflow to this type of pump is a bad idea. Operating an Eheim in a negative-pressure condition is also a bad idea. The impeller will cavitate, dissolved gasses will come out of solution (O2 and CO2), and it might make much more noise. It's not a positive-displacement pump. Centrifugal-design pumps rely on an unobstructed inflow to do their job. If your O-ring is so bad that it leaks then it's time for a new O-ring. The pump is desinged to be placed under the aquarium where inflow pressures can be maximized.


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## Squawkbert (Jan 3, 2007)

guaiac_boy said:


> Restricting the inflow to this type of pump is a bad idea. Operating an Eheim in a negative-pressure condition is also a bad idea. The impeller will cavitate, dissolved gasses will come out of solution (O2 and CO2), and it might make much more noise. It's not a positive-displacement pump. Centrifugal-design pumps rely on an unobstructed inflow to do their job. If your O-ring is so bad that it leaks then it's time for a new O-ring. The pump is desinged to be placed under the aquarium where inflow pressures can be maximized.


My Eheim has always been under the tank and has (since day one) been operating under a modest negative pressure. This should only get less "modest" as the time for backflushing etc. approaches.
One of the reasons people prefer Eheim is that they don't cavitate, even when fed the output from their CO2 tanks/fermenters etc. Limiting the pumps output (IMHO) would be bad for it in the long run as you woul dbe stressing the impellor and you could be switching it to a positive pressure mode (in which leaks are a lot more likely).


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## BryceM (Nov 6, 2005)

So as to not further get away from greenman's original question, I'll simply add that my opinion is based on my background in fluid mechanics and pump design. If anyone has further questions or issues I suggest that they seek a second opinion on the topic from someone knowledgable in the field.

If the canister is under the tank, it is very unlikley that it is operating in a negative-pressure situation, even with a partially closed intake valve.

Partially obstructing the outflow of a pump effectively raises the resistance (or head). This will move you to the right along the pump curve. Most pumps are designed to function perfectly well within their design limits. Centrifugal pumps like the Eheim will not be damaged by continual use even at shutoff head (zero flow).

It is not my intention to pick a fight, but I will emphatically state that it is more harmful to this type of pump to operate with a restricted intake than with a restricted outflow.


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## mofelix15 (Oct 31, 2006)

Im no Rocket scientists but if you wanted too you could get a cheap filstar XP2 i believe that is rated for 40 gallons. I got mine for 60 bucks and 70 shipped. I dont know if i can post a link but just ask and i can show you where. Second all filstar canister filters are capable of running completely dry so if you did dial back one it should be fine because its not under tremendous presure because the actual pump is above the water line in the filter. Maybe im shoooting up a tree but thats my expirence with them.


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## DonaldmBoyer (Aug 18, 2005)

Do a Magnum 350. You can get quick connect valves which will allow you to control the flow, and it would be big enough to handle a 90gallon. They run super-quiet, and you can connect your CO2 to it to get some really nicely dissolved CO2 into your tank.


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## Blacksunshine (Aug 11, 2006)

mofelix15 said:


> Im no Rocket scientists but if you wanted too you could get a cheap filstar XP2 i believe that is rated for 40 gallons. I got mine for 60 bucks and 70 shipped. I dont know if i can post a link but just ask and i can show you where. Second all filstar canister filters are capable of running completely dry so if you did dial back one it should be fine because its not under tremendous presure because the actual pump is above the water line in the filter. Maybe im shoooting up a tree but thats my expirence with them.


Yeah that would also work and be alot cheaper then getting a Pro IIIe. He could get an XP4 for the 90-100 gallon and the XP1 or 2 for the 29 gallon and still spend less then getting the P3e. 
Petsmart also has cupons online for them right now. saves even more $$. over $50 is free shipping.


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## Squawkbert (Jan 3, 2007)

guaiac_boy said:


> ...I'll simply add that my opinion is based on my background in fluid mechanics and pump design...
> 
> If the canister is under the tank, it is very unlikley that it is operating in a negative-pressure situation, even with a partially closed intake valve.
> 
> ...


Not into fighting or flamewars either - just stating what my experience has been. Every time I open my 2215's valves, let it fill & plug it in, the top pulls itself down a little. This is indicative of running the water out a little faster than gravity brings it in. I appreciate that this probably is not the way a designer would go on a first draft for a pump/filter design from a theoretical point of view because having low pressure in the can should lead to outgassing which would lead to impeller disturbances, noise etc. etc. (I deal w/ liquid chromatographs for a living, so I know less than the engineer/designer types but more than some LFS employees about fluid mechanics too).

I agree that restricting the output a little would just mimic having the pump sitting a little lower relative to the bottom of the tank and that this will not harm the pump. My only reason to suggest otherwise is that Eheim probably designed their filter to run under negative pressure intentionally. I think that their impeller is built to "take it" as their vanes are much more stout than others are

Eheim impeller (at right): http://www.advancedaquarist.com/issues/may2002/pr4.htm
Mag impeller: http://ec2.images-amazon.com/images/P/B0002Z7UV0.01-A3N3VAFSB57PBN._SCMZZZZZZZ_.jpg
Fluval impeller: http://rena-aquatics-outlet.planetrena.com/media/Rena-XP-Filstar-Parts/ACC860601.jpg

If they wanted their canisters to run under positive pressure, all they would have to do is increase the diameter of the intake hoses and fittings or mould a restrictor into the output fitting, or they could put the pump on the inlet side (and gum up the impeller faster). I seriously think they wanted negative pressure designed into the filters to minimize the likelyhood that failure of the large o-ring (weakest design element, part most prone to being damaged, wearing out etc. in any canister pump) resulting in a tank dump. Seeing a canister blowing some air into the tank is a lot less stressful than seeing a significant portion of your tank's water on the floor.

If I am correct, then it shouldn't matter if you limit the intake or output side of this canister (limiting the intake would just mimic having some "stuff" building up inside the filter, also normal).

That reminds me - I still need to drill a little hole just below the waterline on my 2215's intake tube!


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## BryceM (Nov 6, 2005)

Eheim did *not* design their pumps to operate under negative pressure. Centrifugal pumps don't work well this way. They specifically state in their instructions that the pump needs to be located under the aquarium. The intake hose is also larger than the return hose. The sole purpose of these design features is to allow it to run in a positive-pressure environment.

It is also impossible for a pump on a closed-loop circuit to allow "water to flow out a little faster than it runs in." The principle of conservation of mass requires the inflow to equal the outflow. If there is a small air pocket at the top of the pump it will enlarge slightly as the pump starts, giving you the false appearance of a negative-pressure situation. As it starts there is a brief transition from static equilibrium to dynamic equilibrium. The pressure inside the cansister does drop as this takes place, but the change is relative. You're most likely going from a +10 pressure (arbitrary units) to a +5 pressure. Less pressure yes, but still positive.

The argument about the quality and function of the O-rings is also without merit since they must perform either way. If they leak, air would be continuously drawn into the pump in a negative-pressure situation until there was sufficient to vapor-lock the impeller. Until the pump is able to expel the air there would be no forward flow, reverting the pump back to a static equilibrium condition with the pressure of the entire water column again existing in the canister. This churn & surge phenomenon is exactly what you observe if the canister isn't positioned below the tank and there is a leak on the inlet side.

If you don't believe me, hook up a tee at the bottom of your intake line, near the connection to the filter. The pressure here should be equal to the pressure inside the canister since they're in direct communication. Put the pump into operation and open the valve. If I'm right, and the pump is operating under positive pressure, you'll see water come out of the line. If I'm wrong, and you're right, air will be drawn into the line. Try it.


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## JG06 (Nov 5, 2006)

I'd buy a Magnum 350 and be done with it. 

If there's too much water movement, drop a Magnum 220 impeller in and move less water. I put them side by side years ago and impeller size was the only real difference I could come up with. Everything else was interchangeable.


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