Can't Get Rid of Green!!

[waterbear]

If your pool has algae I doubt that your TC and your FC are both at the 10-15 ppm range. I suspect that your are testing with OTO (turns yellow in the presence of chlorine) and that only tests total chlorine, not free chlorine. While you might have a high total chlorine reading your FC is probably near 0, if not 0 and it's the free chlorine that kill algae! If the pool has algae then you will have combined chlorine if there is clorine in the pool! IF you are only testing immediately after adding the chlorine then you will possilbly be showing a high chlorine level and no CC but if you test a few hours later you will find the readings have changed a lot! Please let us know how you are testing (OTO--turns yellow and uses a color comparator, DPD--Turns red and uses a comparator, FAS-DPD--titration test that goes from pink to colorless, you count drops) and how often and also how often you are adding chlorine. In the presence of algae free chlorine is cosumed very quickly, which is why the chlorine needs to be added at least 2 or 3 times a day to maintain the level. Also, you have NO cya in your water so your chlorine will burn off in a matter of minutes in the sun! That means your pool has more time without any chlorine than with unless you are adding it every hour througout the day. This will allow the algae to continue to grow.
Finally, don't try and test pH when your chlorine levels are above about 10 ppm because you will get a false high pH reading. Wait until the level drops and then test. I suspect your pH is really much lower than 8.0-8.2!

Edit: also, did you ever change your filter sand after the conversion from baqua last year? If not this might be adding to the problem. Any baquagoo that is trapped in the sand will also consume chlorine and lower the amount available for killing the algae.