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Re:CO2 and Science

Sylvia wrote:

>I believe the thread on CO2 and its effects on fish got completely out of
>hand and irrelevent to tank situations. Technical discussions were centered
>around the knowledge or expertise of the member . . . rather than practical
>discussions on the effect in the tank, and on fish. Some people walked away
>with the understanding that CO2 was not harmful in their tank (with the 
>implied suggestion that it did not need to be so closely monitored) with the
>net result that fish are are now dying. Someone even responded to one post,
>suggesting that it wasn't the CO2 in the tank,  but instead detergent or
>something else that had gotten into the tank, that killed the fish.


Thank's for your well-written post.  It appears that you and I got very
different messages from the discussion.

What I understood is that high CO2 levels may cause some inhibition of
respiration in fish, but it's unlikely that high CO2 levels in the water
would lead directly to symptoms of suffocation.  Acidosis -- both
environmental due to low pH in the water and respiratory due to
accumulation of CO2 in the fish -- was mentioned as a direct effect from
high CO2 in the water.

Also, the point was made very clear that CO2 accumulated *above* the water
can cause asphyxiation by preventing atmospheric oxygen from entering the
water.  The same effect could be obtained from a layer of nitrogen or
argon (for instance) above the water.  It isn't a specific effect of CO2.

In practical terms, that means that if you turned up the CO2 input to your
tank and you found fish gasping at the surface in the morning then you
need to get the top off your tank and get them some fresh air.  Second,
you need to temporarily increase aeration or circulation until the fish
return to normal.  After that you can look to the cause of the problem.  
It may be caused by a number of things - detergent, for instance.  If it
is caused by CO2 then make sure that you can keep the air above the tank
from accumulating CO2 and maybe reduce the CO2 input.  Just turning the
CO2 down or off is unlikely to be the best or quickest route to solving
the problem and it may be completely useless.

For what it's worth, back when I started using CO2 I took the tight glass
tops off my tanks and either left them off or replaced them with lighting
eggcrate cut to fit the top of the tank.  That should prevent CO2 buildup
above the water.

>I believe science is very helpful in keeping fish and planted aquaria,
>obviously. But equally as important, or moreso, is common sense, respect for
>life and keen powers of observation. Unfortunately, as I said, when people
>read these highly technical discussions, they may ignore what common sense
>tells them in deference to the opinions of those that appear more intelligent
>and knowledgeable than themselves.

I believe that science is useless unless the technology is explained so
that people who need to use it can understand it.  Even with a good
explanation inaccurate data from hobby kits or a failure to fully grasp
the context of an idea can quickly turn "good science" into a big waste of
time and money or worse, lead to the death of animals and plants.

Those of us who do get into the technical arguments need to be more
careful to summarize what the arguments mean in non-technical terms.  
That is one of the most difficult things for a technical writer to do.

Roger Miller