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Canister Filters - What Order To Put The Media In


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#1 aimeec

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Posted 16 May 2008 - 04:55 AM

Hi

About a month ago, I replaced an internal power filter with a canister filter on my community tank. The results are fantastic. I dont think I will ever use another type of filter.
I am going to buy another one for my goldfish tank(which currently has a HOB).

Anyway, I was reading a few other posts about canister filters and was wondering what order in the trays should I put the filter media in.

In the canister filter I have there are 3 trays and a space at the bottom. The top has a fine white filter pad, next there are ceramic noodles, then a coarse black filter pad and at the bottom there are a bunch of little plastic spikey ball things. Im not completely sure what they are, the closest thing I can find to them are on Ebay called bio balls.
Are they just a home for bacteria?

Is there a "Best" order for filter medias in a canister filter?
Would you add any different medias to the ones I has mentioned?

Thanks

#2 the biffster

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Posted 16 May 2008 - 05:24 AM

it depends on what type of canister filter you have fluvals on the norm have a sponge at the top
a center section for nitrate sponges and stuff like that and the bottom ceramic rings and stuff like that
i used to run 10 canister filters and you can set them up to work best for you the on i used to have on my gold fish
used to have nylon onion bag type mesh with alfagrog and crushed tufa rock you can set them up as you want them to work for you as long as you don't pack them and stuff that don't brake down and turn in to powder as tony the tiger says there great

#3 waterdrop

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Posted 16 May 2008 - 11:08 AM

Hi aimeec,

I view your question as a bit complicated, although I totally agree about how good cannisters are - its something you begin to realize as you gather more experience with the goals the filtration is trying to achieve.

First bit of complication: You've described the media order without figuring out the flow context! An aquarium filter is a very directional device! Either study the water path and indicate it (best approach) or indicate the exact model (not as good approach because you then need a member who knows that exact filter model) when describing and asking about media order. I'm pretty sure some cannisters push the input water down through the layers and then pull the cleaned water back of past them, whereas other designs take the input water to the bottom first and the pull it through the media stack -- regardless, it is ideal to know your flow order for sure!

Obviously, there is no true ideal media order or we wouldn't all be so pleased with "flexibility." That said, my personal feeling from digesting a lot of threads here on TFF about this is that a typical good order is:
Large Pore Mechanical (sponge) > Ceramic Rings/Tubes (bio) > Ceramic Pebbles (bio) > Small Pore Mech (sponge)

The "design-think" here (I think!) is that you want to first trap larger particles to keep them from blocking off parts of your bacteria in the biomedia (hence the sponge with large holes), then you want the layer of non-collapsable ceramic rings because, when allowed to drop randomly in place, they redirect the water in random directions and keep it from bypassing certain areas or creating "tunnels" through the filter (the ceramic material is also specially designed to be a wonderful porous surface that bacteria perfer for anchoring), then the pebbles come next and just pack a little more densely and less randomly but have an even more porous, more bacteria-philic surface. Finally, designers usually use a final mechanical media (usually a smaller-pore sponge) to catch any small particals that have made it past the middle sections.

Special media (like crushed coral to raise problem pH, or carbon to clean out after medications for a few days) can be used in combination or replacement in a middle section, usually the pebble section. Substituiton of polyfloss (obtainable from big-box stores to stuff pillows) is often used to "polish" (clear-up very small particles) tank water prior to a picture-taking session, or other such situation. All these special things require more monitoring and often shorter in-filter times.

Remember, I've just descibed one scenerio. There are many! It should be noted that a small-pore sponge can harbor bacteria at a similar level to fancy biopebbles or bioballs, perhaps even better! But a sponge must be monitored more closely for deterioration (breakdown of internal structure, allowing tunneling.) Many professionals use simple sponge-only internal filters in numerious situations. The idea of bioballs is simply to combine the random redirection quality of rings, with the highly porous surface of pebble-type media - both rings and bioballs resist over-packing by their very nature - but they give up some total surface area in doing this.

OK, gotta take a coffee break!
~~waterdrop~~

#4 aimeec

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Posted 18 May 2008 - 01:45 AM

Thanks waterdrop. That describes what I wanted to know.

When I bought the filter the media was already packed into the trays, I just removed plastic bags and put them back the way they were, assuming that was right.
It is a AquaOne Aquis 500.

Im not sure what direction the water flows. I was going to take it apart to see if it needed a clean this weekend, now I will also figure out which way the water flows an rearrange the media if necessary. It should be easy - if the intake is above the hole down the middle then I suppose it would send it to the bottom first.

The filter I replaced was one of those internal power filters which was just a bunch of noodles wrapped in a sponge and when you turned it off the take it out to clean the sponge, all the crap would fall off the sides and back into the water.

#5 andywg

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Posted 18 May 2008 - 01:09 PM

Ideally you want all the mechanical filtration first, and then the biological. Having the small pore mechanical last allows some small physical waste to get into the biological media, clogging up the biological media and making it part mechanical in its function and thus reducing its efficiency as biological media.

Some people put fine wool at the end to "polish" the water. Often the reason for not putting it earlier in the filter is that it clogs up quicker. My view is that if your mechanical media clogs up quicker, it is doing its job better.

If you have decent mechanical filtration at the start you will never have to touch the biological. In my wet dry towers I have the water flow out of a pipe onto sponges and then drip through onto the biological media. Due to how well the mechanical media works on the trickle towers I need to rinse the mechanical media under a mains pressure shower head every time I water change. However, I haven't touched the biological media since they were put in some 2 or 3 years ago.

#6 waterdrop

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Posted 18 May 2008 - 03:37 PM

OK, lesson absorbed. Thanks Andy!

#7 OldMan47

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Posted 18 May 2008 - 10:01 PM

For aimeec, the usual arrangement is to have the water come into the filter and somehow get to the bottom of the canister, it then goes up through the various media holders and finally reaches the impeller at the top of the filter where it is pumped back to the tank. When thinking about water flows it is helpful to think of it as from bottom to top, that way its easier to understand the flows instead of thinking about how you come across media as you take it apart to clean it. In all of mine I start with a coarse mechanical followed by a finer mechanical, that way the fine mechanical doesn't plug as fast with big particles. Next is biomedia and finally I get to the impeller but use a very fine polishing pad right in front of the impeller to keep from ruining the impeller with any kind of grit. I only want water in my impeller which means no dust from the carbon if I use carbon is allowed into the impeller. If I ever use carbon it goes after the biomedia and before that final polishing filter. Usually there is no carbon in my filters.




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