I was wondering when you are suppose to add fertilizer to your pond plants. I live in iowa so the weather is still on the cool side. It gets down to about freezing at night but in the 60s and 70s during the days. Both of my lillies are on the bottom of my pond (3 feet deep) have started to grow. They both have about 3 or 4 leaves that have grown about an inch or two. I also have one plant basket with Iris in it and those have grown to about half of their full height they were last summer. Does it matter when you put the fertilizer tablets in?