I have a Blue throat trigger that acts the same way. It is perfectly healthy and once every 3-5 days it will come out and swim around for a few hours and then move back into the shadows. When I first got him, day 1 he laid on his side in a crack for about 6 hours motionless after acclimation. I thought I was going to lose him, but I went lights out for the rest of the day and he was up and swimming around. Currently he lives on his side under an arc shaped rock(shares that space with my purples lobster like a giant pistolshrimp/goby pair), and he lurks in a large cave for most of the day. Pretty funny fish though, just a little shy.
30L w/10gallon sump 4xt5ho; Up and running:125g long, 30g sump, 50g fuge.
"Life is tough, but it's tougher when you're stupid.”
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