He'll eventually reach 12'', so he'll need a much larger tank. And because they can spook real easy, id suggest making sure there is a secure lid on the tank, and he has room to dart around in.
a 55 is the very minimum for one needlefish, although they need to be in a school, for a group of them u will need a 75 gallon tank, a 10 gallon tank is pitifully small because of its length