# I know adding a inline pump/powerhead is bad in a canister filter...but?



## marrow (Feb 4, 2007)

Why would it be harmful to run a powerhead or pump on the outflow of a canister filter.


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## talontsiawd (Oct 19, 2008)

marrow said:


> Why would it be harmful to run a powerhead or pump on the outflow of a canister filter.


I am obviously not clear on this, hence the question. I am not talking about the outflow into the tank (ie-Spray Bar), I am talking about putting it from the outflow of the actual filter.

I have read a few things. First, lets just say you had a pump that is double what the canister puts out. People say that the canister's pump becomes a restriction and gets overdriven. Other people say it creates suction between the pump and the canister's pump as the bigger pump sucks more than the smaller pump does and creates issues. The last one is that the line is already pressurized so the second pump ends up pushing way more than its capacity which creates a lot of internal pressure in the second pump (kind of like using 2 turbo charges in series on an engine-Insane boost). 

I am not really up on this, I have had turbo charged cars so that is the only thing I can really reference. I know that a lot of air pressure with restriction can cause things to pop off, or explode things. I don't know how significant this is with filters at the pressure they give out. I am also not speaking from any experience, just what I have read.


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## Firestarter (Dec 28, 2009)

Unless all pumps are all equal it don't sound like a good idea. If you are just going to run one pump on the inlet of the canister filter and leave all others off then you should be fine as long as the tubing can handle the water flow that you are putting out with the pump.


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## jmhart (Mar 14, 2008)

People do it, but like Firestarter said, unless they flow rates are matched up,one or both of the pumps will operate inefficiently and or malfunction


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## talontsiawd (Oct 19, 2008)

Firestarter said:


> Unless all pumps are all equal it don't sound like a good idea.


The thing is, you see people doing this all the time with DIY canisters that are much weaker in construction (usually) than the filter I am working with. I am not trying to use the pump in my Zoo Med, I would plan to actually take the whole pump out and use something slightly stronger. 

Not to be negative but I would like to hear from people who have concrete evidence as well. It is easy to say don't mess with something because it wasn't made to be messed with but that doesn't mean anything, alot of things can be safely messed with or modified. This may be a good or bad idea, I just want to know in more exact terms than what has been posted.


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## jmhart (Mar 14, 2008)

talontsiawd said:


> I am not trying to use the pump in my Zoo Med, I would plan to actually take the whole pump out and use something slightly stronger.


So, couple of factors will decided what problems this could cause. Essentially what you are talking about doing is modding your Zoomed to be a pressure filter like on a pond system. There will be a maximum flow rate you can use on the zoo med before it causes problems for the pump. To determine this, you'll need to consider the largest source of constriction. Since the filter volume is large, and you can change the tubing, your largest source of constriction is the inlet/outtlet connections on the filter. Therefore, you'll need to make sure these can handle the flow rate of your pump in order to make sure it doesn't cause any problems for the pump. If the pump is overpowered, it'll cavitate, annoying you and ultimately shortening the lifespan of the pump.

I don't know what the I.D of the zoomed inlet/out is, so I can't help you further than that.


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## marrow (Feb 4, 2007)

I have a pump on the outflow of my eheim without issue. My main concern with a planted tank is mechanical filtration more then biological. I have run the eheim 2028 with the external pump and run just the external pump with out issue for three years. I can understand how forcing water into the container could cause problems but I really can not see the problems it will cause with the pump on the outflow. Within reasonable parameters of course, I am not throwing a 1/2 horsepower sump pump on it or anything. I would just throw the damn pump on the outflow and see if it works okay for a trial period. If it is not noisy and seems fine then dont worry about it. The possible calamities that could occur seem pretty low probabilty and low danger anyway. I would ditch the spray bar though why restrict flow when you dont have to.


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## Whiskeyfox (Oct 16, 2009)

Why not just sell the zoo med on S&S and then buy the proper sized canister filter?


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## talontsiawd (Oct 19, 2008)

jmhart said:


> S
> 
> I don't know what the I.D of the zoomed inlet/out is, so I can't help you further than that.


Thanks for the info. The tubing is 1/2, I don't know the inside diameter. I can measure later.



Whiskeyfox said:


> Why not just sell the zoo med on S&S and then buy the proper sized canister filter?


I am thinking about doing that or getting another tank (I have wanted an ADA for awhile). I just figured that this would be possible. I bought the Zoo Med on impulse, it says up to a 30 gallon aquarium so I didn't think much of it. Honestly, it isn't that bad for a 10 gallon (with shrimp), I just thought if this was doable, why not.


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## hbosman (Oct 5, 2006)

It sounds like a good experiment to try. I would try the pump on the outflow and let it "filter" water from a bucket or rubbermaid container, in an area that wouldn't be damaged by a leak. Let it run for a day or so. Use a HOB on the aquarium in the meantime. Half of the fun of this hobby is experimenting and DIYing.


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## MoonFish (Feb 12, 2006)

Eh, hook one up. I'd limit it to like 200gph though because the tubing size will restrict flow. Like you could hook up a bunch of horsepower and get a teeny increase. What's gonna happen? Really?


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## bsmith (Jan 8, 2007)

I have an Iwaki MD-10L inline pre my XP1 for braking up co2 bubbles before they get to the canister. I have never had any issue and it increases output pretty significantly.


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## Ericsmyers21778 (Feb 1, 2021)

talontsiawd said:


> I have read that is is not a good idea at all to add anything like an inline pump or external powerhead with inlets and outlets to a canister filter. The consequences seem to be harmful to explosive.
> 
> I bought a Zoo Med 501 for my 10 gallon and it probably wasn't the best choice. I can live with it if need be. I have an idea though, let me know how this sounds.
> 
> ...


Not true as long as your inline pump attached to your out put hose on canister filter is double the gph on canister filter works great example if 200 gph canister filter put inline pump 400gph or 500gph at most on out put hose it's fine done it before never had any problems saves you hundreds on buying bigger canister filter


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