PYO unfortunately. They were plants that I picked up when I was on field work. I'll see if I can perk up the bit I've still got.
It came from one of the <"ponds in Bristol">, which I surveyed in the summer. The last place I saw it before that was at the <"Steart Marshes project">. It was really common there in some of the rhynes, which are freshwater but high conductivity and nutrient status. It isn't a very common plant.
I keep Frogbit and Ceratopteris as floaters and I've found that when they get too dense they actually "retain" surface bio-film. Normally my surface water skims off over a weir into the filter but dense growth can prevent this. HTH.