My advice, get the pump working and take more pictures, Don't try and clean this pond up in a weekend, Honestly disrupting it's balance completely could be a ticking time bomb. Looking at the pics this pond was poorly thought out and set up. But with so many plants and low stocking level it has become naturally balanced. So for now all those plants are your best friends. READ READ READ, learn as much as you can about filtration and see if there is more than meets the eye, as HTH said sometimes there are filters in the falls, but before cleaning them post pictures, there may be good ways to clean and if done incorrectly again could through the pond in a topsy turbsy spiral. My guess is the pond is probably 1/3-1/2 full of muck in the bottom, that much can carry dangerous bacteria and gasses that if disturbed could kill all the fish. getting good filtration up and going and plenty of oxygen going is a must before even attempting cleaning the bottom end. Once filtration is going correctly them by that time you should have read more and got a better idea of an approach to take to divide the lilies and clean up the pond while still maintaining a good bacteria colony for the pond when cleaned. In all honesty if I were to take that pond and try and fix it it would probably take me 3-6 months of slowly taking care of the problems one by one. First being getting the most out of the filtration I could, then cleaning and balancing the water, then start working on the bottom and hiding the liner and such. You have a decent basic pond to start the project. and it could look fabulous if given the correct attention.
