# Parallel or series?



## d.co (Dec 30, 2011)

I recently picked up two canister filters, one fluval 304 which is the one i originally wanted (for a 33gal setup) and he threw in a fluval 305 for cheap because it's broken (ordered new impeller shaft and self-primer parts already, easy fix) just a curious thought... I've looked it up a bit on the 'net and can't seem to find a good answer/opinion on why one is better then the other, if I wanted to run them both ( may or may not happen, i know it's overkill... but I can adjust the flow-rate, and there can't be too much filtration imo.. just too much current created by the filters) would it be best to set them up in series or parallel?
In series, I would probably use the first filter for mech filtration, and the second filter as bio. In parallel, I would set them up as if they were the only filter, ie adequate mech and bio filtration in each.

Thoughts?
I made a picture.... left is parallel, right is series.


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## Flygirl (Jul 23, 2011)

Hmmm... never thought of trying to attach two filters into one another. I have three on my large planted tank, but each filter works on it's own. Quite like the idea outflows in different areas. Also permits me to have the intake in some areas of lower flow. And it builds redundancy if one fails, the others are independent.

I could see potential issues with the parallel setup as you're funneling double the flow into a single pipe - the filters would be working harder and you would have a much stronger current on the other end. Same issue for your intake, they would have to work harder to pull enough water in. 

The second one, not too sure about it either... I'm sure some others will comment.


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## effox (Apr 21, 2010)

I'd just put it in parallel personally, as I don't know what pumping it into another canister with the resistance would do to either filter.

Cheers,
Chris


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## Adz1 (Apr 21, 2010)

not sure you could actually make it work as the canisters are gravity fed not pumped...


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## 2wheelsx2 (Apr 21, 2010)

Neither. Run them separately. You're not getting more filtration if you do either of these, just bigger capacity for bio. You wouldn't move any more water even if you could make it work because the hose diameter and impeller flow rate would restrict you. if you want a bigger filter, it's best to just a bigger one, but IMO, either of these would be adequate for a 33 gallon.


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## mcrocker (May 29, 2010)

I agree, they will be much less effective when attached together. You can also have more control over flow in your tank if you have 2 inlets and two outlets. You can use that to eliminate dead spots, or to have one filter creating flow and one with a spray bar for surface agitation.

By attaching two filters together you lose some of the redundancy you get by having two. If one stopped running or clogged up, you would at least affect flow through the other one, and possibly damage it by running it when water is not able to flow.


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## d.co (Dec 30, 2011)

Sounds like the general consensus is that two intake and two outputs is the best method... Makes sense, I had my doubts about the two setups I posted but I figured I would post up and ask to see what others thought. New to the hobby and trying to learn all I can..

Anyone know where the best place to go for plumbing? I have some scrap white PCV piping from home depot, but it wouldn't look the greatest as it has markings/print all over it. But what about the intake/output fttings? Strainer for intake? nozzle for output? I was by IPU in burnaby and they don't have any... 
Thanks!


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## 2wheelsx2 (Apr 21, 2010)

I believe you can buy entire intake outlets where they sell Fluval Filters. Maybe KE? Here's a place online: http://www.petsandponds.com/en/aquarium-supplies/c153977/c199366/index.html


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## The Guy (Nov 26, 2010)

They will work better if you run them seperate, better for cleaning as well as you will always have 1 on line while you clean the other one.


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## gklaw (May 31, 2010)

If you really want to run them in series. Try running only one filter, use the other one as a media chamber only.


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## d.co (Dec 30, 2011)

Yeah, I will check out KE.. and then maybe order online if I can't find what i'm looking for. Thanks for the link.

It was just an idea I had when I got the two filters, in the back of my mind something told me neither of them would really work, or be all that effective. I figure for now I will just keep the HOB filter and set up one of the canisters.


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