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Re: Newbie Designs and disrespected substrates

Dennis wrote (quoting yours truly):

>>  Without good aeration the CO2 level in a brightly lit tank will
>> drop to 0 and the pH will go to 9 or more.  Those are hostile
>> conditions for

> um, I'm not following this. I have 2 x 65watt 10k PC flors over a
> 50gal which looks pretty bright to me. I do not use any aeration.
> Surface turbulence is minimal, barely a ripple. pH appears to stay
> stable at 6.8. I need to lower the suggested setting on my CO2
> device because at suggested levels growth is just too fast for me to
> keep up with.

I must not have been clear.  The bit you quoted from me was about the setup 
in which light, occupants and substrate were the most important 
considerations and nutrients were optional.  A setup like that would not 
include added CO2.

If you have bright light on a planted tank without extra CO2 the plants can 
easily consume all available CO2.  The pH goes up to about 8.4 initially then 
if some of the plants or algae in the tank can use bicarbonate as a carbon 
source then the pH will continue to climb.  Plants that can't use bicarbonate 
don't do well.  Fish that can't handle high pH don't do well.  Lots of things 
don't do well.  That condition can be prevented by using a lot of circulation 
and aeration.  Aeration and circualtion add CO2 from the air to the water and 
prevents the CO2 in the water from getting completely consumed.

That isn't usually an issue if the light isn't very bright.  It also is not 
an issue if you add CO2, as you apparently do.  The last two lists in my post 
give my take on the most important elements in a tank with CO2 added.

Roger Miller