Well, this will be a story. I originally had 5 of them, then 2, now 4. But I've never acquired more than 5 different specimens, and all are still alive... :p Let's come back to that.
So first off, it's worth noting that while they're classified as a Halichoeres, we don't necessarily believe that. Everyone thinks they're actually a Macropharyngodon, or at least an early ancestor to the genus. When Randall classified them years back, he thought so too - but one characteristic feature of the Macropharyngodon genus are the pharyngeal teeth - which he did not observe in lapillus. So they found their way into the Halichoeres genus, but everyone still questions that.
Nevertheless, you should think of them as a Macropharyngodon in behavior and treat them as such.With that being said, TTM might be rough.
Now, back to the mysterious story. A few (3?) years ago, I was delightfully humbled by a friend in Mauritius sending me 5 lapillus at zero cost. Truly a gift of friendship. :D At that time, I only had my 190g tank, and with no plans to move or upgrade in sight. Plus, the tank already had a healthy wrasse population in it. Needless to say, I didn't have much of plan when it came to these 5 new fish! So I QT'd all 5 together in a 10g tank, since that seemed like a flawless idea. :p Yes, that really happened, but I certainly don't recommend anyone put 5 fish in a 10g QT. In many ways, I even hate to make a public record of doing such. It's certainly not a sound idea. I recognized this risk and stayed on top of water conditions and water changes.
It took a good week or so for them to settle in, and during that time they were pretty spooky. But once settled in, I didn't find them difficult - all ate mysis with ease. At about 4 weeks into QT and all 5 doing great, I began to make a plan as to what I was going to do with them. I eventually elected to keep 2, give 2 to
@zibba, and ship one to
@Brad Syphus. Brad is another friend of the giver in Mauritius, so that was an easy choice to make. Zibba is a dear friend and at that time lived ~25 min away and had a 450g tank.
Fast forward to present. This past June zibba moved out of state and broke down his tank. He graciously gave me the 2 lapillus back, as I now have a 270g tank after moving across town last year. Both of my lapillus were still female, and only one of his showed some signs of beginning to possibly transition. I felt
pretty comfortable adding his 2 back with my 2 - as comfortable as I could anyway. And my intuition proved good - all 4 are coexisting acceptably in my tank now for the past 3 months. The first few days were a bit touchy, as the smallest lapillus of the group stayed buried for the majority of the day, but we're past those scares now.
And that's the story of how I had 5, then 2, now 4. :p Oh, and Brad still has his too. :D