I only have this one tank with guppies in it..... (originally)..... Their 3ft deep pond is filled only to about 1ft from the brim... yet!!!... I have guppies in with the Swords, (adjacent pond) I have guppies in with the Corydoras... some 3ft away, and I have guppies in with the Platties and Mollies... 4ft away from their tank..... Now how does this happen if it is not wind pollination???