I’ll be honest, I have done nothing special for this little guy. I got him as a hitchhiker on a snail back in November, unfortunately the snail died but I kept the shell and positioned it near the top of the tank in a medium flow area. He’s been sitting pretty ever since and definitely has gotten bigger. Idk if light makes a difference but I run my Red Sea LED50 at 100% blue 60% white in a max nano. Every once and a while my urchin tosses him asunder so I move him back and carefully wedge him to avoid it happening too frequently.
My nutrients have been extremely low and extremely high, right now I am battling very high phosphates (my original hanna checker topped out at 0.9 ppm only to learn that fact after months of thinking they were stable) my snails are falling off the glass semi-regularly so I have started dosing lanthanum chloride to lower (running around 1 ppm when it was north of 2.5 ppm for a long while) and all throughout he's been soaking up and growing.