Hi, have you been diagnosed with cellulitis yet? If it is cellulitis the breakdown of skin can cause a mousy or grape like (fruity) odor. The common bacterial cause of this (staph) could be the problem and gets in by a break in the skin. But since you work in a fish aquarium, a bacteria called Mycobacterium marinum could also be the culprit. So if you can I would see if they can culture this. If it is Mycobacterium marinum it wouldn't respond to the usual antibiotics. So be sure to mention that you were cleaning an aquarium when you got this and wondered if you got Mycobacterium marinum from it. Do you have a fever or swelling of the arm? Also, it is usualy red as well.
Regards,
mkh9