Shorty, Mr. Wizard doesn�t seem to be in, so here�s a shot at why you got shocked. If the air pump was in the tank, and if the tank was glass, the system was insulated, and there was no �ground,� so the water was charged, but it had no current flux except through its original circuit. When you stuck your hand in, you furnished the ground for the circuit, and the result was a memorable zap.
It may not be good science, but I convince myself easily.
Lou
