The only time I ever had a problem was my fault. I had surgery on my hand and arm and even though I tried very hard to be careful before it healed, I ended up with an infection (carrying five gal buckets was a blast! LOL). But other than that, no. I've heard that there might be some things that you can catch from aquariums, but I can't think what they are. I would think as long as you are careful, don't put arms/hand with open wounds in the tank, wash your hands when you're finished working in the tank, don't put hands near eyes/nose/face when you have fish water on them, you should be fine. But I know that I've scraped/cut knuckles on the top edge of the tank when I'm scrubbing the glass, never did anything about it (I am SO not a germaphobe!) and nothing happened.
Why? Do you think you caught something? I know that I've seen long water proof gloves to use when you're working in a tank in some of the fish supply catalogues if you're worried.