This is something very strange that I have yet to the solutiuon to. I have 4 tanks on a 10ft wall of so, a 29 gallon at one end, and a six at the other. I put in several neon tetras into my 29 gallon a few months ago, and they all did well. However the other day, i was cleaning my six gallon guppy breeders, and i saw a glint of something. I looked closer, and saw a neon tetra swimming around. I moved him back to the 29 gallon, and hes been fine. This thing really confuses me, the distance is too far for hime to jump, i dont transfer water between tanks. Also, none of my family knows enough about fish to do play a practical joke like this, theyd think they would accidently kill the neon. This is completely true, and ill give 20 kudos to anyone who can give a good explanation to this.