Azolla fairy moss, good or bad?

As with all things in life, opinions vary, but are generalised as either negative, positive or neutral.
Azolla, more commonly known as Fairy Moss is no exception to this rule.
Azolla fairy Moss is a fast growing floating pond plant which sits on the surface of the water and changes colour from green in the summer months to reddish brown as it becomes colder.
There are many pond owners /fish keepers who would cringe at the thought of having Azolla fairy moss in their pond. This I believe can be attributed to it`s fast spreading capabilities, Once you have it you will find it very hard to get rid of.
Personally, and from my own experience I have found that Azolla fairy moss in my pond can be very beneficial. One of it`s greatest benefits is that it quickly provides shade. If your pond is in an open position with out any natural shade, algae can quickly take hold and turn the water green.
Azolla fairy moss shades out the sun causing the algae to die and sink to the bottom where the filtration can remove it.
It must be remembered however, that whilst this is good for reducing algae, Azolla fairy moss will also block out the sun light to your other plants causing them to suffer and therefor its spread has to be controlled. Also too much Azolla fairy moss can hamper fish feeding.
Azolla fairy moss also makes it more difficult for predators to see the fish which is particular advantageous if you live by the coast and are blighted with seagulls or similar as in my case.
I all find that my koi seem to enjoy eating Azolla fairy moss which I do not think is a bad thing.
I have heard fish keepers say that their fish do not touch it, perhaps I am an exception!
I like to keep at least half of my pond surface clear and currently have a small surplus of Azolla fairy moss which I am selling on ebay.
If interested you can find it here:- Azolla Fairy Moss