Mechanical filtration question

[lael01]

I have a little theory on the subject. I don't know if it's true, so somebody correct me if I'm wrong. Power filters actually have motors to 'suck' in the water, while (as I understand it from fluvals manual) canisters rely more on gravity. While there is a motor in the canister, it mainly pumps water out, thus creating a current and helping the water get 'sucked' in. (if any of this made sense great if not let me know and I'll try to re-explain)

You are actually right in a sense, the impeller contained in the canister is mostly for the return of water to the tank. Whilst this also maintains suction and flow to the filter, the 'head' (height from height of pump to height of water outlet) that pump has, IMO means that often a powerhead/filter will work better in the tank at removing junk. It has zero head and therefore is pumping more water.... and creating more current....

 

[RTR]

It will only be more efficient if the system itself is designed to be more efficient. The head of a canister filter in normal operation (intake and return to the same water level) is zero. And the rarely justifiied assumptions seem to be included that HOBs motors and impellers are equal to those on good canisters - which I find doubtful at best. Media porosity and placement, possible by-pass, and media volume are major factors in the function of any mechanical filter.

 

[anonapersona]

Why do people say power filters are better than canisters for mechanical
filtration ?

A Filstar XP2 replaced one of my two Penguin 330 power filters. With the use of filter floss in the XP2, it traps A LOT more junk then my 2 Penguin 330's combined.

I also have an Aquaclear filter on another tank, I add a 1 1/2 inch of floss on top on the sponge and then Bio Max. The floss traps A LOT of junk that
the sponge doesn't. The floss get really brown and dirty after 2 weeks.

I think your question is mis-stated. Your best result seems to be when using filter floss, regardless of the sort of filter involved. Floss is a very fine media, and so ought to pick up more "dirt".

There are several things acting together to make up ease of use and effectiveness of a filter. Mechanical filtration is mostly dependant on flow, for it takes good flow rates to pull debris toward the filter from all the parts of the tank. Pump flow is only one item, though, for fast flow will suck more debris from the tank but if flow through the filter media is also fast, it may simply blow right through whatever sponge or pad is used as media. Media porosity is another item, and a finer media will create more pressure loss as it plugs up so the media needs to be either a very large volume and cross section to flow, ie canister, or needs to be serviced more frequently, ie HOB filter.

If you ever want to go back to using the Penguin 330s, there are new clamshell type frames that you can load with sponge or floss of your choosing. I use this in my 330 and I think it is great. I can rinse the pads several times before I toss them. And, with the biowheels, I find it helps to shake them well in used tank water every week or so to get off any clumps of bio-slime that otherwise would be ready to break off and float in my tank. Eventually you will see this same sort of stuff floating in the tank with XP filters if you neglect to clean the output tube once in awhile, for bio-slime will sluff off of that output tube and be left to float in the tank also.