It appears you have a few things to consider. Since the black dot never disappeared, you have next to no stabilizer (CYA) in the water. Before you add any stabilizer though, review both A & B below and perform as it applies (have some chlorine/bleach ready):
A) Add enough chlorine/bleach to get the FC to 10.
Check it in 10 minutes. If the FC fell below 5, increase it right away back to 10 and test again in 10 minutes. Repeat as necessary. Once it holds at 5 or more, add stabilizer for a CYA goal of 30, increase the FC to "12" and begin a
SLAM Process until you pass all 3 criteria.
B) If the FC held between 5-10 on the first try with no problem, then go ahead and add stabilizer for a CYA goal of 30 and balance according to the
FC/CYA Levels. Use the sock-soaking method to dissolve it. You can test the CYA the next day.
- Also increase the pH and TA a bit. Since both are low, you can use some soda ash (washing soda). If you don't have that, try some Borax. If all you have right now is baking soda, that will increase the TA and may help the pH start to rise as well. Try to get the TA to about 50-70. If you had to do item A above (SLAM), then the pH only needs to make it to about 7.0-7.2. If you don't need to SLAM (item B), then let the pH climb into the mid 7s.
You'll need chlorine/regular bleach. There's just no way around that, especially if you need more for multiple 10-min tests or a SLAM. Try Walmart's Pool Essentials in the outdoor section or their Great Value laundry bleach (plan/regular). Also try Lowe's or Home Depot's pool section. Good luck!
