Who the hell have you heard that off, it's a new one on me. The closest you'll ever see to a fish suffering from anything like compared to the bends is when fishermen drag deep sea cod for example up from the depths too quickly. Their swim bladders become huge due to decreased pressure at sea level and can be seen hanging out of their mouths. Also at very high altitude you can suffer from the bends. In a fish tank?....about 2ft deep?....at sea level (give or take)? i'd say your fish are pretty safe.