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re: DIY co2 having no effect

ChuckW7160 at aol_com writes:
> This actually brings up a good question. What would one consider to be a good
> mechanical/biological filter for a planted tank? For many reasons I've always
> used biowheels for my non planted tanks. Due to the large surface area of the
> wheel, and the constant flow of water over them they make an ideal place for
> water to de-gas. This production of oxygen rich, and co2 poor water is great
> for the fish, but less than ideal for the plants. I thought about using a
> whisper type of filter with the removable cartridge but I've thought about one
> major drawback. when you periodically replace the cartridge you are throwing
> away all of your nitrifying bacteria, thus throwing your tank out of balance.
> How do you get around this problem? Has anyone come up with a way to provide a
> stable bacteria bed without having excessive gas exchange? Any help would be
> greatly appreciated.

> Charles

The solution I adopted for that problem is an external canister filter filled
with just mechanical and bio media. No carbon, peat, etc. I use a Fluval
with the first basket filled with ceramic pellets and the two other baskets
holding floss and ceramic balls. The biological effect is the same, or even
better, I had before with a high-flow UGF covering the full extent of the
tank. But surface agitation is nill, since I installed the spray bar in a
vertical position and with the output holes pointing parallel to the front
glass. So there is plenty of water circulation all across the tank but no
surface rippling at all. Adding a home-made surface skimmer made the surface
look exactly like a mirror when viewing from below, which gives a very nice

Since the bio media is made up of several individual pieces, one can 
clean/replace just a few a time, on a rotating basis. Thus the filter can
hold almost all of its biological capacity and be kept clean at the same time.

BTW, I had the same "CO2 having no effect" symptoms when I first assembled
the tank about 3 months ago. The cause wasn't surface agitation, but 
buffering caused by some decorative whitish gravel (packaged specifically
for aquarium use !). I tested all materials used as decorations and substrate
separately, letting a handful of each rest in a water bowl for a couple of 
days and then testing KH and GH. After I re-assembled the tank without adding 
the whitish stones, the pH dropped consistently to 6.6 - 6.8, from a tap
value of 7.2 - 7.3, using the same DIY CO2 setup and rate as before.

Ivo Busko
Baltimore, MD