Insufficient chlorine can allow a pool to harbor a lot of algae that is kind of hidden in plane sight. Many of us describe our pool water as sparkling. When it looses that sparkle, something is happening. I keep mine open all year long and let it go a little this spring as the water started to warm. Without me noticing it went from sparkling, to dull to a little cloudy before I noticed. In all of these conditions it still would have been classified as "clear pretty water" to most folks. I conducted an and proved that something was growing in the water as I failed the test. While my didn't take long, I still needed to eradicate the algae in the water.
I say all of this because the next step down the road had I not caught it would have been green. So yes, it can go green quickly, but things were growing before that time.
You still need to add a signature line to your profile giving us your pool specifics like size, gallons surface and equipment specs and provide us with some GOOD test results from one of our recommended test kits. 4 lbs. of WHAT did you add?
I went to the pool store, had my water tested and went with their recommendations. My test kit didn't come in yet. I put 4 lbs of Chloe brite shock with 2 quarts if phos free and ran my pump for 24 hrs
That's alright, we can get you sorted, and what we do is really easy with a little knowledge and some good test results. We can help with Both. With the Green Pool you'll need to SLAM it. It a process of repeated adding of Chlorine to a higher level and keeping it there until the Algae is dead and the pool is clear.
You need a good test kit on the way first. For a Green Pool the best value is the TF100. The K2006C Is also a good kit, but you'll need extra reagents and the 100XL has them at a much better price per test.
Next is knowledge. All that is here in Pool School and the first place to go is the ABCs. Eveything you need to know is in PS and there are many around who will enjoy helping you through with any questions.
For sure you wont need the Phosphate products, so dont add those yet. Take them back or hold the receipt, and perhaps trade for something else. Once we have some reliable numbers from you, we can offer suggestions.
The links you need are also in my sig line below here: