Funny you say that, I use RSCP too. I've been dealing with this for about a month now. Long, stringy, snotty growth that waves from the rock. It grows on everything. Overflow, powerhead, clogs my return pump, clogs my sump sock. If I slip up even for a day on rotating my sump socks with this stuff, then the sponge in my Eheim 1260 becomes completely clogged, throwing off my water levels. Beananimal overflow will run dry, sucking in air and gurgling, return in sump will be flooded and my Tunze ATO alarm will go off. When this happens, evaporation takes place in my external box and the salinity climbs, since the return level stays the same/rises preventing auto top off of freshwater. This stuff is really evil.
In the beginning, I thought okay, it's probably something in the rock and it will just run its course. A few years experience in freshwater has taught me "when in doubt, water change". I started doing 20 - 25% weekly WCs. Two weeks ago, I spent 6 hours cleaning every nook of rock in my tank. I blew the rocks off with a powerhead, turned my RW-4s up on max to keep it suspended in the water column, and did a water change via pump in the display. I figured I could make a big dent in its population by removing it directly. I skimmed wet, emptied the cup daily and rotated filter socks regularly. Tank was CLEAN clean when I was done. Despite my best effort, it was back with a vengeance in 48 hours, worse than before. With each water change, I notice an explosion of growth. I cleaned the sponge in my return pump last Saturday (10/3) and Monday morning (10/5) I woke up to my Tunze ATO alarm going off again. This goes against everything i've ever learned in the aquarium hobby, i'm completely stumped. I bought Dr. Tim's Waste Away after reading that article and began dosing on 10/3. I did two half doses per the article and today was the first full dose. I've noticed more of the stringy snot floating in the water, like it's dislodging from the rock on its own. Coincidence? I'm not sure but I really, really hope it's working. This is such a discouraging thing to go through after being so excited to get into reefing. I accumulated gear over months and was chomping at the bit to get my tank up and running. Now that it is, it just seems like a never ending game of tank maintenance that leads to worse growth than the day before. My parameters are in check, no detectable PO4 per Hanna, 1 or 2 ppm nitrate, no algae growth besides a few streaks of diatoms. So frustrating.