SnapperUSC,
A peacock mantis will be too big for your nano cube, and would require at minimum a 20 long. I have a much smaller N. wennerae in my nano cube. That is the species commonly found in Tampa Bay Saltwater live rock. They sell individual mantis shrimp and also sell other marine animals and macroalgae native to Florida, so maybe you could order from them. I wouldn't worry about N. wenn hurting the tank.
I have a nice 12 gallon nano cube on my desk. It's been set up a while. Besides the mantis shrimp, I have:
1-2 inch DSB
about 8-10 lbs Fiji live rock
Halimeda and Caulerpa macroalgae
assorted frags (many will eventually outgrow the tank):
toadstool mushroom
turbinaria (2)
galaxea
hairy mushroom
green mushroom
orange polyps (zoanthids)
yellow polyps
brown polyps (Palyzoa)
torch coral
frogspawn coral
Rose Bubble Tip Anemone (quickly outgrowing tank) and small clone of regular BTA
Many of the frags came from
www.seacrop.com, CPR frags. I am very happy with their quality, price and service. I recommend selecting your own frag rather than getting the nano frag pack to make sure you get suitable, hardy species for a nano cube.
For your first time reef tank, consider mostly moderate light requiring soft corals, mushrooms and polyps. Later consider some hardy stony corals after you have some experience. Fanworms are really nice, hardy additions as well. Be prepared for anything NOT a mushroom, polyp or colonial soft coral to outgrow the tank at some time. You can frag/thin and trade with other hobbyists, set up a bigger tank eventually, or sell/trade for store credit at some LFS.
Watch the temperature, it is easy for nanos to overheat, especially in hot climates.
As for my work, I am a department head over product development, marketing and technical support in the Living Materials (= all the animals and plants, genetics, biotech) Department of a company that supplies biological science materials to schools. My degree is actually a Ph.D. in plant genetics, but I have a pretty good general biology background.
My advice is to plan for a career doing something you really love. That advice won't guarantee you will make a lot of money, but you may be lucky enough to look forward to Monday during your working life, as I usually do.

At the same time, be knowledgeable and realistic about existing career opportunities. A lot of time to actually work in biology, you need to get at least a master's degree or a Ph.D. as well as relevant experience. The problem with herpetology and field biology (like marine biology) is that you might have limited in career options in these fields. If those areas are your passions, though, you will find a way to make it work. Try to get experience as an undergrad working in labs or companies that are relevant to your interests. You'll have a chance to get some good references for grad school or a job, and you will get a chance to find out if the reality of working in that area is really your passion.
Good luck with the tank and school!
Lisa