I am very tempted to buy these plants which will supposedly, once established, "aid the clarity of water in a fishpond by feeding on suspended algae".

Now here is a definite market opening up! The green water eating water lily. I should buy them all I think and start a nursery (again) - selling these wonderful plants.

But then doubt creeps in - as it does - and I wonder if it sounds too good to be true? Has it really got these little algae filtering devices somewhere in its hidden gills? Or is this just a marketing ploy - like so many others on this well known auction site? I will watch with interest the auction number 116830976, that's for sure!

LOL, that's funny. They actually just outcompete the algae for food and light which results in a clearer pond. They do a great job at it, too!

Utricularia feed on microbes in the water. I dont know if this includes free floating algae.

no it does not include algae. Bladderworts (Utricularia) are carnivorous.