My daughter and I have two right now, need to get a couple more. We lost our big strawberry recently, he was our first one. He was already really big when we got him, they didn't have shells big enough for him at the store tank so he was making do. I immediately bought the biggest shell I could find and he happily moved in. He was about the size of a very large store sized apricot or small nectarine. I was a little scared to get any more because the store has been carrying little guys and he was so big. I was very sad when he died, but now we can add some new friends.
There are lots of websites with helpful suggestions for fresh foods that hermies will love. I also add in a few tiny pieces of egg shell for them to nibble on for the calcium.
Sounds like you are off to a good start with your new crabitat. You may not see them much during the day, but you will probably hear them at night wandering around and knocking their shells against the glass. Mine also make a weird squak like sound at night sometimes. We hadn't noticed it until we spend a week out of town with family and I had them living in a little critter keeper for the week. I couldn't leave them behind, but couldn't take the whole crabitat so they had to make do with temporary quarters. That whole week, we kept hearing a squak sound coming from the cage.
Did you get some extra shells? Hermies love shopping around and changing homes.
I think you can fit around 4 hermies in your crabitat. That's how many I'm planning on having. Also, I don't keep my coconut substrate soaking wet, I just keep it moist. It's moist, but fluffy I guess, LOL. I did a change out today and some rearranging and when I put the crabs back in, they went nuts. They ran all over, climbed up and down the "hill", ate, explored some more. They finally settle down and found a resting area.