That looks awesome so far! Love the castle idea, very clever. I will be attentively watching this thread to hear about it as you go. I've seen a bunch of DIY tips for these, but never actually heard from someone as they progressed through. I want to make one of these for my 29 Gal
. My hopes for it are to put a small tunnel in the back of it so I can pull water from the opposite end of the tank than the side that my filter is on. But I love the idea of being able to put caves on the walls other than just being restricted to the floor.