Years ago I grew one of these water crowfoots (probably Ranunculus aquatilis) in a pond,very beautiful, but have never seen any similar relatives available for aquarium use despite being sold as pond oxygenators. I originally thought it was a temperature thing, but now I am not so sure as varieties (or closely related species) grow in some hot countries. I have found reference that the foliage is somewhat toxic or even poisonous, might this be the reason it is not generally used in aquariums (small volume of water to dilute toxins) or would this only be of concern if you had plant eating fish?