[APD] Re: non CO2 tanks do not have constant CO2

[Thomas Barr <tcbiii at earthlink_net>]

>Tom said, in part, " . . . No, non CO2 tanks do not have constant CO2. Quite
>the opposite. . . "

>But, in a low tech, subsoil-and-peat substrate environment, one in which the
>subsoil had been soaked for two weeks before using, why would the available
>CO2 (or C) vary significantly in the short term, say, the first month?  The
>only sources of it would be the atmosphere, the respiration of the fish, and
>the decay of the substrate, none of which would vary much in that short
>term.

You might slap your head.
What do plants do during the daylight?
Remove CO2=> Causes the pH to shoot upwards.
Measure the pH on a fully planted non CO2 tank.

At night the they do not take up CO2, atmospheric CO2 and respiration adds the CO2 and the tank's CO2 re equilibrates. pH variations can 2-4 full pH units in natural ecosystems and about 1.5-2 in non CO2 tanks everyday.  
This diurnal variation occurs within tidepools, lakes, ocean, anywhere where there is high primary producing occuring in water. Both algae and plants cause this to occur. We add CO2 to stop this decline/change in CO2 levels and to amply the plants(and algae in some cases) enzymes that fix CO2.

>Assuming that to be true, the way to treat algae in such a tank would not be
>to increase the CO2, since by definition that would be impossible, but
>rather to limit the nutrients by water changes until the plants have taken
>hold and can do that themselves.  Right?

No.
Perhaps CO2 limited, it'll be very tough to have co limition is reference to CO2, it's 40+ % of the biomass.

The tank will never be non limited as far as the algae are concerned.
The same basic principles apply to a CO2 enriched tank as they do to a non CO2 tank concerning algae.
Algae, just like plants(embryophytes/Charophyceans) like CO2 also. But realtive to biomass, the plants need far more CO2. Both take about 5-7 days to adapt to HCO3 use(if the plant is able, most all algae can in some form or another or simply need so little CO2 there's always enough).

So it's an issue of rate of growth.
Non CO2 tanks work primarily for the same reason a CO2 enriched tank does.
But the RATE is slower for both plants and algae.
So the algae is much easier to keep ahead of if you let things go. 
Herbivores do more damage to algae per critter also.

The tank still has plenty of plant biomass. You don't prune it very much, inputs=outputs, that is still the same, it's the RATE that you have changed, nothing more.
 
Plant growth is also slower and while the plant is limited in terms of CO2 for most of the day, so are the algae, 
Since growth RATE is slower, I add more organic material to the substrate since it would take 1-2 years to build up naturally wereas a CO2 enriched tank would make a mess and it's Rate is much faster and so is the rate of organic material build up/production.

Fish food is added since the rate is slow enough to allow fish waste alone(or very close) to supply all the plant's needs at this limited(CO2)

>Bill

Regards, 
Tom Barr


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