I've been chugging along, shocked until it was gone, but as soon as the chlorine drifts back to normal range it grows right back. Think I'm just going to shock weekly and vac daily in the hopes that it doesn't grow too fast (it probably will). At the end of the pool season, I can SLAM again but thinking I should hold the mustard algae levels for more than 24 hours? We have followed all of the SLAM directions at this point (twice), we have deep cleaned the sand, backwashed as needed, vacuumed the floor daily, brushed the walls daily, cleaned the ladder(if algae is inside of the ladder, I don't know what I'm supposed to do about that) and pool floats before we put them in the water, left them in the water for shocking. I don't know what this stuff is, all I know is that it grows, because if I don't keep it at shock level it continues to grow more each day.