I have a 500 gallon pond with some goldfish and koi. Last year i had water hyacinths and some Lillie's. the hyathinths did really well but the Lillie's never did good and turned yellow. So with the Lillie's now sprouting up i wanted to do something to help it. I was wondering if miracle grow plant food spikes would help the Lillie's and at the same time be safe for the fish. Please help!!!