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Something to think about


Quick summary... I think that some algae problems might be a direct effect
of poor plant growth (not to be mistaken from the case where algae causes
poor plant growth).

I have two "sister" tanks - very similar setups sitting side-by-side
receiving similar care and carrying similar populations of both plants and
critters.  They're very simple setups that I use for testing methods for
low-input aquarium care.

I've got straight-leaved val planted in both tanks, but for six months or
so the val in one tank has been stunted.  The runners are very short, so
the plants are right next to each other, they grow only a few inches high
and they're very light green - almost white.  Soon after they started this
stunted growth pattern the tank also developed a mild plague of hair
algae.  All, in all it's pretty ugly.

Despite the stunted growth, the val in this tank bubbles vigorously -
especially after water changes.  So while the plants don't grow very well
there certainly doesn't seem to be anything wrong with their ability to
photosynthesize, as evidenced by the bubbles.

I'm not the first on this list to observe this sort of behavior and wonder
where - if the plants aren't growing - all the carbohydrates produced by
the photosynthesis are ending up.  I have read in technical literature
that some aquatic plants - mostly algae - might "leak" some of the
carbohydrates produced in photosynthesis.  I've also read that algae can
use carbohydrates in the water in place of synthesizing it themselves.

Last week while cleaning that tank I started wondering if the stunted val
might be leaking carbohydrates that are feeding the algae.  To test the
idea I removed all of the val - there was a lot of it - and replanted just
5 or 6 of the larger plants.  I also dragged out a little of the hair
algae, but I didn't go out of my way to clean it all out.

I watched the tank closely this week and by mid-week it appeared that the
hair algae was not growing back at the rate it normally does.  Today when
I cleaned the tank the only hair algae in the tank was a detached tuft
drifting around at the back of the tank.  The algae didn't disappear
entirely on its own, as there are three flag fish in the tank.  But the
flag fish have never before been able to keep up with the algae.

Has anyone else seen algae problems go away when stunted or poor-growing
plants were removed from a tank?  If it's true that poor-growing but
actively photosynthesising plants can feed algae, then we may have an
alternate explanation for some otherwise mysterious hair algae problems
that we hear about on this list.

Roger Miller