Living in Florida i am lucky that mangrove wood is everywhere. There is a shop here locally called Driftwood Decor. I can give any of you the phone number if you want to arrange to have huge peices shipped to you. They have a yard completely full of mangrove, cypress, and some other wood i can't remember. All sizes and shapes. I find it hard to find anything that would fit a tank smaller than 50 gallons, but you could always break the peice or something. It would probably be very expensive, two branchy peices for my 50 gallon cost me $20. Much cheaper than my LFS though. A very large peice could be in the hundreds easily. PM me if you want the number i dont get the email reminders at the house i am at right now.