Ultra low nutrients from over cleaning your water can be just as detrimental as too high. LPS like detectable nitrate/phosphate, and all corals need nitrate and phosphate for growth/coloration. Mature reefs are ultra low nutrient because the corals are sucking everything out of the water. Stick with softies and LPS at the beginning as they will be happy in a dirtier system or parameter swings. A $10 acro frag could have been on the way out before you bought it.