Nymphoides seems quite sensitive to nutrient levels. When nutrients get a bit low, it starts making leaves without the little bump from which the plantlet will grow near the blade . Refresh nutrients, and the next leaf will have the little bump. I got the little flower buds when I boosted nitrogen, phosphorus, and iron. Now I have to rip out a whole tank full of Myriophyllum mattogrosense which is overwhelming everything to get the Nymphoides back under ideal conditions.
This is my first experience with M. mattogrosense. I had no idea that it was such a rapid grower or such a take-over plant. Every branch produces numerous side branches, and they all grow horizontally and smother everything else. Also, the branches that are covered over with other branches don't stop, and soon you have an impenetrable mass. This Myriophyllum may get banished to a gallon jar on the windowsill, where it can join Potamogeton perfoliatus, Zosterella dubia and other plants that can take over a 20 gallon in one week.