Why is your tiger tale sea horse turning green?

Answer 1

Just from what I've observed with my lined seahorses, they seem to change color as a signal to their partner that they are ready to mate. Also, seahorses are ambush predators, so they have a better chance of catching food and not getting eaten themselves if they can change color to camouflage themselves. They are very slow swimmers, compared to most of the other fish species and would be very vulnerable to attack.