I need Dwarf Puffer fish help!?

I just recently purchased a 5 gal hexagon tank and am interested in dwarf puffers. Would it be better to have 2 in the tank for company or do they like to be alone? I purchased a cave with plants attached, a coral reef and some green leaves(all fake) since I have heard they like interesting environments. Also, I have read that they are extremely sensitive to the water quality. I have had fish before but since it is a new tank, any suggestions? I really would rather not buy cheap fish to cycle the tank faster, I will feel bad if they do die :( Thanks in advance!