My 15 year old black plaster pool looks pretty good after all these years. I acid washed some of it recently and looks even better. Don't need new plaster (yet).

But there are several plaster cracks in corners (no leaks) that grow whiteish crystal blobs that i assume is the gunite underneath reacting to the water it sees from/through the micro cracks. Some of the cracks are many inches long. If not for these "white crystal bumps" and streaks and stains by the cracks the pool would look almost new.

Is there any way too remove this growth easily ( I sand it off now with a stone) and then prevent it from coming back? Do i have a water balance problem and/or must I seal the tiny cracks in plaster? I was hoping that next time i drain to acid wash the whole pool there is some simple adhesive or coating applied locally that can seal these off. Better yet this is just a water balance issue? I usually have the pool balanced per recommendations but do see hardness low at times. Balancing now...

At opening 2 weeks ago: CYA=0, TA=170ppm, Cu=0, Iron=0, CH=160, ph=8.0, FAC=1, TAC=.2 diff and very green due to warm spring.

p.s. My wife is suggesting we paint pool in lieu of re-plaster if i can't fix the quickly worsening year to year crack white lines and bumps. Is that a bad idea? I see so many divergent opinions on that. The cracks might show right through the paint anyway!