Thanks everyone for the replies. In summary it seems that azolla is only a
problem in a mature well-stocked pond in the Spring before other plants get
going; and if you don't have azolla then you will likely have an algae bloom
anyway in the Spring. The advantage of azolla is that you can remove and
compost it before it dies and pollutes the pond - which you cannot easily do
with algae - especially as my pond will be a wildlife pond without a pump or
filter.

But since I am constructing a new pond, it is likely in the first few years
to be a bit sparse on competing plants and the azolla may run wild. So, in
conclusion, better not get the plants from the source that has azolla.

thanks for your help, Davy

"Davy" wrote in message ...
I am building a 16sq m wildlife pond in Wiltshire, England and someone who
is thinning out their pond in September has offered a whole range of
plants
to get me started.
Unfortunately, their pond has azolla. Is this likely to be a problem?
There are some horrific photos on the web of large ponds and ditches
completely choked with azolla. But a garden pond owner who has azolla
states that their other plants keep it down to just a very small patch. I
imagine they compete for nutrients.
I don't expect any fertiliser runoff to enter the pond but I do expect to
top it up with tapwater. I suspect that azolla is only a problem when
there
is excess nutrient in the water?

Anybody with experience?

thanks, Davy