Alleochemicals and algae

I'd like to buy in to the theory that it's the alleochemicals in plants that
help them outcompete algae, but my sowrdplant (the one I think may have been
inhibiting the growth of my ludwigia) has hair algae growing on the ends of
the older leaves.  Is it possible that some plants release chemicals that
affect other plants but NOT algae?  Is this another reason why slow-growing
plants such as echinodorus should not be used in a new tank when you're
especially trying to avoid those initial algae outbreaks?

Also, regarding algae: Tonid, have you checked your nitrates and phosphates.
I find that when I keep nitrates below 10 ppm I have little/no red algae


P.S.  Regarding FISHROOM: I've not visited on Saturdays recently, but about
a month ago, after the first few succesful meetings were anounced on the list,
I went there on a Saturday afternoon & no-one was there.  I'll try again this
weekend & hope to see others there too.