This is the only MA at the Walmart here, and it sells for $6.88. Home Depot sells the 31% for $9.99. A few people have said it is 20%. I have used a bottle, and that number corresponds well with the pH change in my pool. It's basically 2/3 the strength at 2/3 the costs, and it keeps me from having to make a special trip to Home Depot.
I cannot say for sure if it has anything else in it, but I went with it based on responses to my post. After 1 bottle, I've noticed no side effects. I do wish it would list exact ingredients.
That’s good to know. I will say if you have a pool store near by to check with them. I just bought a 2 pack for 11.99 at 30%. Last year a Walmart near us had a 2 pack of the 20% but I haven’t seen it in the pool aisle this year yet.