Hello samdaman,
i have 10 red mangroves in my 36 gal sump and i am verry happy with this. The waterlevel in the sump is nearly 15cm ( 6 inches ) with 4 inches live sand. I recive the mangroves 9 months ago with a lengt of 7 to 8 inches and without sheets. Today, i have the problem, thats the mangroves are expandet to the double size and have 6 to 8 sheet pairs. Next month, i will change again to junger and smaler plants and i will buildup a new separte open mangroven tank for my old plants. Here is a verry interessting website about species and handling of mangroves.
http://www.mangrove.de This site is also written in englich.
Best regards
Mike