I am looking after a neighbours very big outdoor pond for 10 days whilst he is on holiday. The pond is full of Koi Carp and other fish. During this very hot weather the pond has filled with green algae and the pump keeps blocking up; I am having to clean the pump out 2 or 3 times a day; I have bought some barley hay and put that in and tried to scoop out as much of the algae as I can. I notice that the amount of water seems to have gone down, about an inch of the liner is showing; is it safe to top the water up from the hose pipe which is connected to the domestic water supply? Very grateful for any help that you can give me please.