He's about 7-8 inches and it's a 90 gallon tank with about a 30 gallon sump I feed it frozen blood worms out of a turkey baster and it hasn't yet he only sticks his head out of the decoration
Mine would come out in the late evening but they also had the tank all to themselves, so there were no other fish to spook them. If it's eating, I wouldn't worry much. It will come out when it starts to get bigger and more comfortable. You can try feeding it red wigglers and see if it will take those. It's best to get it on a variety of foods but that can take time and some of these guys are so stubborn that they never end up taking any other foods.
Just make sure there aren't any decorations that it can become trapped in. It's possible that as they grow, the holes to their hiding spots might become too small and eventually they might not be able to get out.
As far as tank size goes, you will probably need a larger tank for it within the next year or two. Once these guys start eating, which yours already has, they start growing a lot. Within two years it could easily be 24" long, and will still have a ways to go. They usually grow to around 30", but it's not at all uncommon to see them reach up to 40". A 90 gallon is just not big enough for it as it grows that large.
