I had a 10 gallon tank with a couple pieces of lr and 8 mangroves. I loved it. Actually, I still have it set up, but now it's a 20 gallon tank with a couple pieces of lr, and 8 dead mangroves.., so, the best advise I can give you is not to try transplanting them after they are established. I was really bummed when they died. I expected them to lose their leaves after the transplant, but wasn't expecting them to die.
If you set up a tank with a sandbed, and a bit of lr, mangroves, and one or two small fish it makes a nice display. You won't need a filter really, although a p. skimmer, or cannister filter with carbon would go a long way toward keeping the water from yellowing. As far as lighting, I started with a single MH, but the mangroves all began to bunch up and grow towards the light. I ended up using a couple LOA fixtures spaced out and then the mangroves started to branch out more.
It won't be easy to keep corals in such a tank, mostly because of lighting. The lights will need to be fairly high for the mangroves. Although you could put the mangroves on one end of the tank, and then hang a light source lower for corals on the other end of the tank.
Try to pick a fish that will be out swimming a lot. I started with a royal gramma, but he hid all the time. The pseudo chromis I tried next was nice, but he ended up jumping. Now, I have a Sgt. Major damsel in there. His stripes stand out among the mangroves and he looks pretty cool in there. alghough he's gotten kinda large for the tank.
good luck,
Dan
