i have a filter and a pump and a fountain and also i use a type of algae reducer thing (like a syrup) , also there is a shade cloth over the pond. How can i clean all the rocks that have algae on them, so far i have cleaned abit of them one by one with a sponge, can i put them in boiling water to kill the algae any suggestions??????? thankkyouu (10 points best answer)

I am using an old milk can as a water fountain and want it to look like milk is spilling out of the can continuously, but the substance used to color the water can not be thick to clog a circulation pump and it needs to be non-toxic incase the children get into it becouse it will be at ground level.