Feeding Swans

We have a bonded pair of swans and 5 cygnets in our local pond. The pond itself is surrounded by grass and then a perimeter 4 ft fence.  Access can’t be granted to the water  

the swans are mostly in the water but have nests in the grass and do occasionally wander in the grass too


 I can’t reach the water when I try to throw any food in (too far away) but i also don’t want to attract rats by putting food in the grass area

Looking for advice on what to feed them please