Question: what are the best oxygenating plants for a small pond?
Answer: For spring and winter water-crowfoot (Ranunculus aquatilis) is to be recommended and in summer and autumn hornwort (Ceratophyllum demersum), pondweed or waterweed are to be preferred. Other well-known oxygenating plants are mare's-tail (Hippuris vulgaris) and water violet (Hottonia palustris).