Water Lilies Leaf Rotting

Question
I have a new pond which I put in in April this year,  It is about 10 feet long, seven foot at the widest point and about two and a half feet deep.  There is also  a shelf running all round the pond about ten inches below the surface.

I planted some water lilies some of which I had been given and some of which I purchased from a nursery.  Almost all of these have sent up leaves but the leaves have turned yellow and have a black "rotting" patch in the center. Some of the leaves have died off completely.  The lilies were planted in proper aquatic plastic boxes with an aquatic liner in soil which was specially for pond plants.  Other plants on the shelves and on the bottom are flourishing.  The pond has six golden Rudd about 5 inches long but I don't think they have affected the lilies.

Can you tell me how to correct the lily rot, what I have done wrong, if anything, and how to avoid the problem in the future.

Many thanks

Peter M

Answer
Your problem could be a natural leaf cycle, whee the lily is trying to grow new leaves, but I think it may be crown rot caused by a fungus. I would pluck the dead leaves off of the plant and get them out of my pond incase it is a fungus, if it a fungus it can spread to other life in the pond.  

Many factors could be at play here.

Your potting soil: maybe has too much acid in it. (I use a mis of regular "natural" garden soil, sand, and peagravel for my plant pots. I use more gravel than anything. It works great for me.

Temp Change: If you are having fast changes or major changes in the temp. in your pond this may cause some plants to have problems.

Algae destroyer: If you added an algae killer the your pond recently this can sometimes cause problem for plant life.

I hope this helps you some.