Hello reefers. I've bought yesterday my first sand sifting goby. It's a six spot goby Valenciennea sexguttata. At first he stayed up all night swimming up and down the tank. Thankfully it didn't jump. When the other fish woke up he went and occupied the small cave you see in the photo and he didn't come out since then. I tried to feed him mysis shrimp, pellets and AF plankton but he didn't respond to anything. Should I be worried or eventually he will be alright? What do you think?