~ jan wrote:

On Sat, 9 Aug 2008 22:00:31 EDT, kathy wrote:

All algae thrives on sun, fresh water, fish waste, plant waste,
blown in dirt.

We must STOP this myth, pleasssse. "The fresh water myth." We have
people in the koi club with 24/7 flow thru, changing out 10%/day. There is
NO green water in their ponds. Fuzzy good algae on the sides yes, but not
suspended algae (makes the water green).

Algae thrives on sun and nutrient rich water. Fresh water, from the tap,
is not nutrient rich. And unbalanced pond also causes green water.

I haven't actually come across this myth before, but I guess I can
understand how it came about. Some "fresh" water could be high in either
phosphates or nitrates (especially if the water comes from shallow wells -
otoh, chloramine treated water is a source of nitrogen). So I guess _some_
people's "fresh" water could trigger algal blooms. But on the whole I'd
have to agree the problem isn't fresh water.

I'll add to the list above, though, that "dirt" per se isn't of any value to
algae. Only if it comes with phosphates and nitrates is it going to
matter.

Algae needs _only_ phosphate, nitrogen and sunlight. A common cause of
algae is fertilizer imbalance. Potassium isn't required for algae growth,
but is for plants. If you don't have enough potassium (like, perhaps, the
person with yellowing water hyacinth) the plants can't use all the nitrogen
and phosphorus - but the algae can, and so you get algae blooms.
--
derek