Bird bath algae?

[Tim Bo]

My parents have a small concrete bird bath that gets about 8-10 hours of sun a day. I noticed that the inside of it had a red algae growing under the water. Does someone know why red algae would grow there and not ie. green?

[RTR]

I get brown, red, and green algae in my birdbath. It may be that either the brown or the red is the major one, but I haven't really tracked that. But it is hard to get more eutrophic than a birdbath.

[Tim Bo]

Thanks for the reply RTR. Eutrophic it definitely is! I did some searching since my initial post and found a page by Steve Durr, A common inhabitant of bird baths. Apparently, the micro-organism is called Haematococcus pluvialis, some kind of photosynthetic flagellate. Here's the link : http://www.microscopy-uk.org.uk/mag/artjan99/haem.html
Though it doesn't say why this would manifest itself instead of other types...

[Tim Bo]

A collegue has just told me that he puts copper pennies in the water and that these stop algae from forming in his bird bath...?

[RTR]

Copper might well slow/reduce the algae, but copper, although required in trace amounts, is toxic beyond that very low level. I do not know the txicity for birds, but I would certainly not use the technique - there would be little reason to provide water if it is of potential harm to the critters being watered.

[Tim Bo]

Yep, that's what I figured.
I told my parents about my 'sudden' interest in their birdbath, and their reply was, "what birdbath?" :)