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Re: Balancing fish and plants

on 01:48 PM 9/27/99 , Aquatic Plants Digest wrote:

 >1) moderately soft and acidic water is incompatible with CO2

...unless you do something to increase the KH, which may or may not be good 
for your particular plants and fish.

 >2) in a heavily planted tank with constant CO2, the standard advice to
 >eliminate all surface agitation is lethal to many species of fish, at least
 >in the conditions I keep them in: moderately high stocking levels and large

I agree again. After I eliminated surface agitation, the fish were still 
gasping for air at the surface in the morning, even when the plants had 
been bubbling furiously the night before - and if the plants had a bad day 
for any reason, it caused even more stress and occasionally killed a fish. 
I got suspicious after I discovered that every time a fish died, it 
happened in the early morning before the lights came on, when the oxygen 
levels were at their lowest.

I ended up putting an airstone on a timer to turn on for a few hours every 
night. This wouldn't be a good idea except that my water has a high KH, so 
there is very little pH variation. Now the fish are happy, and I haven't 
had a death since. It takes care of surface scum and duckweed, too.

I think lots of plant enthusiasts let oxygen levels get a bit low. I've 
read many stories about SAEs jumping the night after a major pruning (i.e. 
less plants means less oxygen) and I'm sure it would explain a lot of other 
problems. I think I'm going to stick to the "high KH and aeration at night" 
school of thought for my tanks (especially with my tap water.)

Of course, I stock tanks heavily compared to some plant people. A 
lightly-stocked tank could get away with oxygen from the plants, but mine 
has trouble. (I do stay under one inch of fish per gallon, though.)

michael moncur   mgm at starlingtech_com   http://www.starlingtech.com/
"You can pretend to be serious; you can't pretend to be witty."
                 -- Sacha Guitry