it grows anywhere coral can grow, and it isnt a sign of bad water params, its a sign that your corals aren't going to bleach out anytime soon. be lifting out the minor offenders, use a pocket knife to detail dislodge from anchor points, and you can q-tip on some peroxide on the former algae anchor spots before rinsing off/setting back in. like dentistry. dont control algae via water param changes, if your animals miss it/u have to fix it manually.