I've been dosing AB+ for a couple of months. About 3 weeks ago several SPS corals started STN at the base of the corals. Admitedly, I don't dose very much, maybe 15ml x2 a week as a treat. While trying to figure out why some corals were STN'ing, I noticed the following message in the directions that come with the AB+ bottle, - "Signs of underdosing in a low nutrient system are bleaching of the corals from the base upwards", which is exactly what mine were doing. And, my tank runs about 3 Nitrate and near-zero phosphates. Can anyone explain why AB+ has this affect? According the the directions I should be dosing 50ml/day for my size tank, which means I would be going through 3 500ml bottles/month, which is cost prohibative.