Hi and Welcome!!! The only chemical I ever add is declor when I add water. Agreed with everyone above. Eventually the algae will mostly go away. It just needs time. I think it's hard to do for a lot of new pond owners because you want to show off your new pond to family and friends and it doesn't look great when it looks green. If you have floating algae you can remove it mechanically by using a net or a bristle brush to scoop it up, but never scrub it off the liner. Algae is actually a wonder drug in a lot of ways... it provides camouflage from predators and reduces stress in your fish, a great natural food source for your fish, and it synthesizes harmful wastes and excess nutrients in the water into less harmful components. When your pond "cycles" beneficial bacteria will build up sufficiently that the algae will lose their food source and mostly disappear. Unfortunately when you put in chemicals it make it much harder for the beneficial bacteria to get established. Good luck!