well i don't know would need more details, liek light water and how often u do a water change or dose.
I just started my nano and all i had on the rockz were little specs of purple (only one rock) and now it spread to the others and there are specs all over the place and the main one that had it to begin with, now has little circles of purple=P and my tanks only been running 2 weeks\
I by the way do a 5 gallon water change every sunday
out of my 28 gallon nano. and i also drip kalkwasser for my evaporation.
i don't have the answer, but my rock is encrusted with it, and started with my first tank w/ regular 30 wt bulbs. i had dosed with alk and calcicum at the time..don't remember why, i was new and that was was they told me to do. i think my ph. is low
Oh yeah the obvious answer is if you never had any you will not be growing any. It's easier to grow when you have some in your tank already. If all you have in your tank is about a quarter size don't expect even with optimal water conditions and lighting to have it cover the entire tank overnight. If the amount you have is about doubleing every couple of week you should be on a good pace. You need to judge you growth rate as compared to what you had previously and not in relation to the entire tank.
Definately DON'T use Purple up, as it's ummm garbage. Once your levels, alk/ca/mg are good you shouldnt have problems. Just give it time, some tanks take longer than others.
thanks my alk 2.0 cal 450 mg 1400 give or take. I was it starting to grow but it stoped akter a water change i do 35g every 3 weeks from my 120g + 25g water in the sump