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Re: Plant Bubbles
Ken,
You're getting close to the answer. The reason the plants bubble any
time is simple. They are producing oxygen, and the water is saturated
with oxygen. It's as simple as that. When you do a water change,
generally the water is mixed with warmer water, either before or after
it enters the tank. Warm water can carry less oxygen than cold water,
so the oxygen gets forced out of the colder water. If the warm water is
already saturated with oxygen, the oxygen bubbles off (ever wonder why a
bucket of warm water, especially in winter, is cloudy, then clears?
That's why.) If the warm water is not already saturated with oxygen,
the oxygen is transferred into the unsaturated water. This results in a
higher level of oxygen in the tank, so when the plants try to crap out
some oxygen, it emerges as bubbles, rather than dissolving in the water.
The same mechanism governs the bubbles you saw when sunlight hit your
tank. The rate of photsynthesis increased, the plants needed to get rid
of oxygen and saturated the water, then any more oxygen had to be
bubbled off.
Tanks with strongly oxygenating filters will have more bubbles than
those without. I used to run a trickle filter on my tank. Each
afternoon the plants would have streams of bubbles rising off of most of
the leaves. Now I run powerheads with sponges and little surface
agitation. The plants are growing faster than with the trickle filter,
but I seldom have many bubbles, and except after water changes in the
winter, I never have streams of bubbles all over the tank.
I seriously doubt that any nutrient carried in a water change could have
such a rapid and dramatic effect. If nutrients were the cause, it would
stand to reason that bubbling would increase dramatically and
immediately after fertilizer is added. I've never seen that, have you?
Finally, "does that mean that I need more than 3 watts per gallon?" If
your plant growth rate is satisfactory, you are getting enough light.
If you want faster growth, more light MIGHT help, but it might also
result in a tremendous growth rate... for your algae. It may also be
that your lights are old and no longer putting off all the light they
should. If it's just the bubbles you want, try a trickle filter or
oxygen reactor. (Or maybe one of those bubbling sunken chests with a
skeleton! ;-) But that will drive off the CO2 you are injecting, so you
may decrease the plant growth rate. If you feel you must change things,
I suggest you try one change at a time, and evaluate for at least a
month before going on to the next change.
Steve Garinger
in Lawrence, KS where the wind is blowing us awaaaaaayyyy...