Hi,
If you have not yet used the tank, I would take it back for exchange for another shape. I had a 30 gallon fresh water hexagon once and it was very difficult to clean because of the depth. Other problems are small surface area for gas exchange, poor circulation near the bottom, limited space for fish and creatures that like to hang out in rocks near the bottom, and I know your arm can't be 30 inches long. I think the number of fish will be a lot more limited in number due to a lot of fish have larger horizontal territories vs. vertical territories, meaning you could keep more livestock happy in a shorter tank with more bottom and surface area. The fish just like more room to swim side to side vs. up and down. Also, there is the problem of hanging filters and skimmers on the short sides of the hexagon tanks.
If you cannot take it back, I am sorry.....these are just my thoughts on that shape of a tank. I am not meaning to degrade your tank or to make you feel bad. It's just that I have also read in fish books, and seen for myself that even though these deep and narrow tanks may look nice, they have a lot of draw backs.
Good luck to you, Lesley