Hi, and welcome!!
The algae growth you're having is because you're not keeping your chlorine levels high enough for your CYA level. With a CYA of 40, you will need to shock your pool (we recommend plain, unscented bleach for this) up to 15 ppm, and hold it there by testing and adding more bleach as needed to hold that 15 ppm level until the algae is all gone. Once you can go from sundown one night until just before sunup the next morning, then you can let your chlorine drift back down to the 3-6 ppm range, but no lower, otherwise you'll end up with algae again.
When your pH is low, you add Borax to raise it--not baking soda. The baking soda is used to raise your alk, which is fine where it is.
How are you getting your chem readings--are they drop-based or strips? If you don't have one, do yourself a favor and get your own drop-based test kit. Using pool store readings, which are designed to sell chemicals, is an expensive, and often not reliable, way to get your water tested. We recommend the K-2006 kit (see the link in my sig), which will test for everything you need, accurately, and help you take control over your pool.
Don't put anymore algae treatment or cheap algaecides in the pool--they're just creating another chlorine demand for you to overcome, and you want all your chlorine to be available for the algae.
Again, welcome to the forum!!
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