Hi Red;

1. Go ahead and add a SINGLE dose of HEDP -- use whatever dose the label says.

2. Is the slime all gone, now? (Your borax is getting high enough, to help with that, by the way. If you've added over 12 boxes, you should be in the 'will make a difference' zone!)

3. To manage chlorine levels, with your CYA as high as it is, you'll need a K-1515. See the test kit page linked in my signature. The Best Guess page (also in my sig) will explain why. The alternative is to drain and refill, which I don't particularly recommend.

4. If the slime is all gone, you need to let your chlorine drop. But, with stabilizer that high it would also be to add a dose of polyquat, every 3 days. A quart contains 1.4lbs of polyquat (100%) so it has 1.4 x 9 = 12 ppm for your pool. 2 - 3 ppm doses are effective, or about 1 cup at a time. Depending on how quickly we can proceed, you may need another quart, since you can't have chlorine in the pool at the same time you have ascorbic acid.

5. Once the chlorine is below 0.5, and the HEDP and polyquat are both in the pool, you can add the ascorbic acid. Start with a 1lb dose, and see if that lifts all the stains. If it does, you can begin rechlorinating slowly. But continue to use polyquat till you have the chlorine up to Best Guess levels.

6. If you are going to use the CuLator to remove the iron from your pool water, you can put it in now, UNDER the skimmer sock. (The HEDP only holds it in the water -- as the HEDP breaks down, some of the iron will end up on your filter, and be backwashed out. But, some may re-stain your pool.)

BUT, before you start trying to add ascorbic acid, the slime MUST be gone, you must have a reasonable idea of what your CYA levels are, and you must have a K-1515.

Good luck