Hello, I've been running a small aquaponics setup for a few weeks now, using guppies and ghost shrimp. For a while now I have been trying to get the guppies to eat out of my hand with mixed success (they don't fear me but the flakes and blood worms float out of my hand.) Recently I've noticed that a few of the guppies (various ages, breeds, and both males and females) will swim up to my hand and rub their faces against it. Sometimes they'll do this several times in a row before swimming off. At first I thought they may have been sick or something, but it's been several days and they're all perfectly fine. They aren't rubbing against any of the plants, walls, or other objects (though they seem to enjoy pulling up some of the smaller plants. Haven't figured out why but they look to be having fun) just my hands. Does anyone have any ideas as to what's going on?