Please don't go throwing anything in yet. Ponds can take up to 5 years to settle down, once you get some plants, marginals and lillies in there (if it's big enough), you will start to get a good balance. The plants will remove nitrates and phosphates produced by the fish and the lillies will give enough surface cover to stop the water going too green.
Your pond will probably go through several phases...you'll get the "pea soup" effect of green water as the day lengths increase and the sun gets warmer. Blanket weed is another pain too. Whatever you do....don't go flushing the pond through with the hosepipe...all the nasties in the tap water will feed the green water and blanket weed. Instead, try to just see it through and get the balance between sunlight, fish, plants and nutrients right. Of course you won't know this is happening until you get there but eventually, you'll have a lovely, thriving pond with gin clear water.
if you don't want fish....maybe to keep the balance right you can add half a dozen sticklebacks. fascinating little fish that just keep things ticking along....and you wont even know they're there.
Good luck