I honestly find it’s every so often when they’re truly hungry that they go for CUC. It’s also most commonly the larger species like
Halichoeres chloropterus that go for CUC. But there is ways around it;
Species of snail that are nocturnal, have hard shells, can flip themselves and also ones that hide in the sand are perfect IME. But as mentioned above always having a certain amount of CUC is great - snails often die for no reason so it’ll be great to replenish them.
Also good morning to those on the other side of the lake from one of my favourite flashers/fairies in my collection!