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CO2 and low light fish CO2 additions

> I posted a similar question a few weeks ago and received no responses, so
> I'll rephrase it in this context:  Instead of adding bottled CO2 to a low
> light aquarium, could a similar result be obtained by adding more fish?  Or
> wouldn't this be feasible?

I'd tend to say "Not feasible". Bacteria decomposition will provide a fair
amount of CO2. But they need O2 to do this. O2 is supplied by adding CO2 for
the plants to give off higher levels of O2 for the bacteria etc. Fish also
need a fair amount of O2. Fish alone cannot make up for the CO2 needs of the
plants unless your trying a non CO2 approach in which case HCO3(KH) will
also contribute a large share of the carbon supply also.
Adding enough fish to make a noticeable difference will add too many fish
first off(and your night time respiration levels will include plants, fish,
bacteria and algae etc and no input of O2 except from the air), it would add
a ton of NH4(algae & bacterial decomposition(more O2 depletion).
Try it sometime. See if it works, I mean just go ahead and _kill all your
fish_ from low O2 levels and high NH4, NO2 levels:-) Even adding CO2 etc
this doesn't work well when the plants are growing at optimum levels. They
simply cannot take in enough NH4 that the fish produce with algae creeping
in. You introduce other problems(NH4) and the exchange or 02 and CO2 is not
equal between fish and plants. Fish produce CO2 all the time, plants do not
add O2 all the time. The result will be dead fish or in a milder case, lots
of algae.  
> I guess I'm looking for a bubbles-per-minute inches-of-fish equivalency.

I doubt you can figure this generally, but perhaps on a specific type of
fish. Most catfish don't need much O2, many others do. I think you'll find
that they contribute only very slightly to the input of CO2 in any system.

Everyone seems to think they can weasel around the CO2 issue.

I see too many post that start out like "I don't want to use CO2.......but I
want a nice planted tank like so and so's" "Why do I have algae" etc.

You can do it but you are limited, you don't add things to the water column
like traces or other fertilizers, you add flourite or if you prefer(I sure
don't) soil and make a nice deep layer 4inches or so deep, add algae eaters
and a few fish slowly, 1-3 watts a gallon(T-12,T-8s), moderately hard
water(or add baking soda , CaCO3 etc) some floating plants hopefully, plant
heavy from the start, feed fish well and regularly, don't do water changes
often, do not add trace elements/fertilizers *except* fish food. Do not move
your plants around! Manual removal occasionally of algae. This can and is
Pick either adding CO2 GAS only additions or go down the above road.

I think adding DIY to a low light tank is much easier than adding DIY to a
higher light tank. Try that. It works better than nothing at all.

Tom Barr

> Thanks.
> Bill