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Re: notes on hair algae

On Wed, 1 Sep 1999, Ed Street wrote:

> A local nursery where I visit often for hair algae (sae's and yamato's)
> has a serious growth of hair algae, they stated they can't do anything to
> get rid of it (yea right)  Well today when I was getting my pound of algae
> I also got some water samples.  There's 4 ponds all the same material,
> seems the same fish/snail load, #1 and #2 has more light than #3 and #4.
> The samples I took was from #2 and #4.
> Sample from both ponds are: pH 6.7, co2 25ppm, ammonia 0ppm, alkalinity 2
> dGH, general hardness 5 dGH, nitrates 0ppm, iron < 0.05ppm and copper
> 0ppm.  The owner stated that it's been awhile since he fertilized any of
> them.

Using the KH-pH-CO2 chart with pH 6.7 and alkalinity 2, I get CO2 of about
12 ppm, not 25, but just the same that strikes me as being rather high
for a brightly lit pond with plants and algae.  It implies to me either a
high respiration rate in the pond (pollution and/or very high fish load)
or that the plants and algae were not photosynthesizing.

> The troubling section that I find interesting here is the usual
> iron/nitrates (am currenty out of my phosphate kit) are very very low but
> yet theres a serious outbreak of hair algae. It grows in mats that smother
> other plants.

Perhaps under the conditions you measured the hair algae are dying off.
If not, then...

If the ammonia and nitrate were actually zero (and probably nitrite zero
as well) then growth of floating algae would be impossible.  Some form of
dissolved fixed nitrogen is necessary.  Perhaps the low nitrogen content
is a temporary condition, or the low point in a daily cycle?

Even with iron levels somewhere below 50 ppb the dissolved iron levels are
only likely to limit algae growth if the phosphate concentration is high.
If phosphates aren't high then the phosphates should be growth limiting.

It seems to me that the association between hair algae and iron might be
unique to the PMDD regime where it is often reported but it's difficult
for me to explain even in that context.  My worst hair algae problems have
come in tanks that were never dosed with iron.  I've even seen some
varieties of hair algae growing in tanks were rooted plants were showing
symptoms of iron deficiency.

Roger Miller