# How does water flow in a Canister Filter? Top to bottom or bottom to top?



## miogpsrocks (Sep 3, 2015)

I have a 402B canister filter from I think Sun Sun, its kind of a popular filter on Ebay which is a Chinese knockoff of the Fluval and probably the German canister filters. 

I can't figure out how the water is suppose to flow and what type of media I place in what cartridge ? 

As far as I can tell, the water enters and exits 1 inch apart on the top of the canister. I don't understand how water is suppose to travel though this big thing. 

Can anyone please help me out on the hydrodynamics of a canister filter? I would like to know the placement of the activated carbon. 

Thanks.


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## Immortal1 (Feb 18, 2015)

Intake water enters at the top, travels by some type of internal tube (have not opened a SunSun filter, but have 2 AquaTop filters)to the bottom of the canister. The water then rises thru the various media to the top where it rises into the impeller and forced out the output tube back into the tank.

In general, the course filter is at the bottom. The a fine filter. Then your biomedia at the top (where the canister water is the supposedly the cleanest). Most of us don't use the carbon media on a regular basis.

Bump, your filter is basically the same as my AquaTop. The water enters at the top, then spirals around the UV bulb on its way to the bottom of the canister.


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## miogpsrocks (Sep 3, 2015)

Immortal1 said:


> Intake water enters at the top, travels by some type of internal tube (have not opened a SunSun filter, but have 2 AquaTop filters)to the bottom of the canister. The water then rises thru the various media to the top where it rises into the impeller and forced out the output tube back into the tank.
> 
> In general, the course filter is at the bottom. The a fine filter. Then your biomedia at the top (where the canister water is the supposedly the cleanest). Most of us don't use the carbon media on a regular basis.
> 
> Bump, your filter is basically the same as my AquaTop. The water enters at the top, then spirals around the UV bulb on its way to the bottom of the canister.


Yes, I think Aquatop and sunsun are basically the same thing. ( might even be 100% the same) 

So the first cartridge is the very bottom and the last cartridge is on the top? So the activated carbon goes on the top cartridge and the filter floss goes on the bottom?

What goes last ? Biomedia or activated carbon? 
Thanks.


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## Immortal1 (Feb 18, 2015)

Probably a toss up on which is last. I would probably put the bio media last as I don't want dirty water clogging it up.


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## PlantedRich (Jul 21, 2010)

Some thought on how and why you place the media is useful because it does depend on which filter and what meadia you may want to use. One of the good things about canisters is that you can swap and change the media to make it fit what your tank needs. As mentioned many do not find carbon not worth the hassle and leave it out except for special times. Carbon is fine for removing tiny things like what cause color or for removing medicine when done treating. But these tiny pores also stop up really easy to the carbon needs to be changed out, often after only a few weeks. After stopped up, the carbon just blocks flow so needs to be removed or replaced. In canisters, that is often not what we want as they can goes for months if no carbon is used. 
The flow depends on which filter is used. In some the water goes to the bottom and works it's way up but in others like the Eheim2071 thru 2076, there is an extra layer of really course foam at the top. This lets you pop open the top and change out the heavy grung without pulling the whole media set. These filters run it through the top course sponge, then down to the bottom before working back up and out. Best to check the manuals on each filter when it is not obvious. For the basic filter brands, it often runs to the bottom, through course media and then gradually finer. Where the bio-media falls depends on the trays available. You do want the bio to be kept clean but Eheim has it nearer the top and the really fine filter floss at the very top and last. But none of this is set in stone and some run filters for purely mechanical or far more bio depending on what that specific tank needs. Some playing and experience with the tank and filter will show you what works best for you.
IF I were using carbon to remove meds or color, I would want it on top so that I did not have to dig to the bottom every few weeks to get the "blanket, blank" stuff out every few weeks. 
I leave it out.


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