Feeding pond plants

For a small to medium pond there is no need to add fertilizer to the planting compost as a matter of course. It may have a detrimental affect on the pond as it will dissolve quickly and cloud the water as it will feed the algae with mineral salts.
For large waterlilies in large areas of water nutrients can be added, but in small areas of water you should wait at least a year before using any. The best option then is to add a low release fertilizer in the form of a sachet that can be pushed into the container. Only use this type of sachet, recommended for waterlilies as unlike normal fertilizer it will not dissolve rapidly and lessens the risk of speeding the algae growth.
Oxygenators will not need feeding as they get all of their nutrients from the water.
The vigorous forms of marginals may become starved of nutrients quickly however, as they are grown in restricted containers. Instead of feeding these plants in their containers it is best to remove them each year, divide them and replant into fresh compost. This also keeps the plant healthier and stops them looking ragged and starved in the centre, as all the new growth is on the outside of the crown.