I have an Eheim 2028, which is a completely closed canister filter. I have
never detected anything but zero nitrites and/or ammonia levels after the
tank was cycled, so my guess is that I have quite a bit of excess
biofiltration capacity also.

I have an in-tank diffuser, a cylindrical vertical tube with bio-balls
inside and a fine-mist airstone that emits CO2 from underneath the
bio-balls. Water circulates through the bottom of the tube to the top, over
the bio-balls, and out an outlet in the top of the diffuser. This thing
requires cleaning every 5 or 6 weeks. The powerhead that circulates water
through it requires maintenance more often than that. This idea of
injecting CO2 into the filter is appealing because it sounds like I would no
longer have to service my diffuser. I presume the added CO2 does not
necessities cleaning the canister more often. (I cannot see how that would
happen..)

Anyhow, thanks for your reply.

-Bruce Geist


"Chuck Gadd" wrote in message
...
On Tue, 14 Jan 2003 21:20:56 -0500, "Bruce Geist"
wrote:

I am wondering if it is ever possible that CO2 in the filter would
inhibit
nitrifying bacteria. (I doubt it, but I am curious..) Have you checked
your
nitrites and ammonia levels since making this change?

Adding CO2 to the water in no way reduces the O2 level of the water.
In fact, most tanks with CO2 injection will have a measurably higher
level of O2 due to photosynthesis. So, the bacteria have just as
much, or more O2 available to them.

The one place where CO2 could reduce biofiltration would be in a
trickle wet/dry setup. In my wet/dry, the trickle chamber is fairly
well sealed, and probably contains higher than normal levels of CO2.
So I probably have reduced bio-filtration because of CO2, but wet/dry
filters provide so much bio-filtration that the small reduction
doesn't have an effect.



Chuck Gadd
http://www.csd.net/~cgadd/aqua