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RE: Packing canister filters

Mike G. asked about the proper packing for canister filters and worries
about the inclusion of Chemi-Pure (carbon and ion exchange resin combo).

Mike, Chemi-Pure has been on the market for a loooonnnnnngggggg time. It is
a good product, for a specific purpose. It is a chemical filter media, not a
biological one (or, at least it should not be allowed to become a biological
medium by being left in place undisturbed for a long time). Whenever I use
it on any of my own tanks, I always use it last, after mechanical and
biological filtration. I also only use it for a specific reason and for a
limited time, e.g. if I notice too many tannins leaching into the water
column in a soil substrate tank. But I never run Chemi-Pure, or any carbon,
for more than about a week or at most two (rinse it well after use and put
it back in the bottle it came in - you can re-use it).

Because breaking down a canister filter is such a chore, I don't put it
inside of the canister - I've rigged a system where the a portion of the
outflow from the canister filter flows through a bag of Chemi-Pure before
entering the tank. In this way, it is easier to pull the Chemi-Pure out of
the system when the color has been removed from the water column.

Ehfisubstrate, the media missing from your setup, is not actually rock - it
is a sintered glass material which is exclusively biological in action. It
is not designed for mechanical filtration and the water should have passed
through some good mechanical media prior to encountering the ehfisubstrate.
The sintered structure of ehfisubstrate (similar in nature to Siporax) gives
a huge internal surface area for biological filtration. In my own Eheim
2260, I have 5 L of the ceramic noodles on the bottom, 5 L of lava rock in
the middle, and then 5 L of ehfisubstrate on top. The noodles stop (or at
least break up) large particles of detritus which will get stopped
(hopefully) by the smaller granules of the lava rock (ehfilav). In actual
practice, not everything gets filtered out, and some particulate does hit
the ehfisubstrate in my setup, but since the Eheim 2260 has a backflush
feature, I am able to control this so it doesn't become a problem.

With a smaller canister filter (the 2260 holds 17 L of media), not as much
effort is required to change the media and clean everything, so I'd suggest
that you use a layer of the easter grass between the  gross mechanical media
and the ehfisubstrate. This should keep your biological media free from
getting clogged with dirt.

About your bubble situation - this seems to be "one of those things" that
goes with the territory when dealing with canister filters. I find that mine
gurgles only when dirty - it's a signal to me that cavitation is happening
inside due to too much flow resrtiction, and it's time to clean the blasted
thing. I have no experience in feeding CO2 into my canister filter - I use
an in-tank counter current reactor for that.

James Purchase