I had an arrow crab and ate all mine... I did take him back eventually because they are super mean and extremely territorial. It ripped an arm off my coral banded! I used to call him *******
Do NOT put in with seahorses! Also, seahorses are a very hard and sensitive animal to care for so if you're fairly new to the game I'd wait a while before diving in...
I don’t have any seahorses yet, tank is still cycling