explain why the pond does not get hot?
they chew the ugger and ewws of the dog
I'm surprised that you wish to remove water lillies from a pond with fish. They do a great job using up poisons and providing shade. Most people pay a small fortune to get them to grow in their pond(s). The only way I know of to remove them is to actually get in the pond and physically lift them out.
Water + light + nitrogen + oxygen will always produce algae/water plants. That is natures way of keeping water clean. The easiest of the above to control is the light. If you reduce the light getting to the water surface by shading a section that will help. Placing aquatic plants like water lillies in there to cover some surface area can also help.
Ripples on the surface of a pond are an example of wave motion.
because you're stupid
Yes but the ducks eat all bugs. Well not all bugs.
The lily pond at its focal point with the most beautiful water lilies.
Pond plants like water lillies and flag irises ,watercress is also fine.
Surface of water
the answer is 28 days. if 1 lily covers the whole pond on the 30th day, then it covered half the pond on the 29th day and a quarter of the pond on the 28th day. 2 lilys on the 28th day, each covering a quarter of the pond, cover a total surface area of half the pond.
Fish need oxygen to live. Many swim to the surface to take a gulp of air. Also, a plastic cover would alter the temperature of the pond, particularly if there is sunlight nearby. Imagine it like sitting in a hot car with the windows rolled up.
the high density level of the pond was due to the many streams running into it and also the unusual number of lillies.