My Sevs allow me to pet them, they pop right up to the top like "Hey mom, give us some love, we see you pet the dogs all day, so our turn."
All the fish, regardless which tank, have taken a liking to nibbling on my arm when I am in the tanks doing maintenance. I have a fair amount of freckles, so they aim for them. Everyone from the itty bitty Tetras to the 8" Sevs.
The Shrimp can't be left out, they are funny, without fail when I am pruning their tank they congregate on my hand/arm, They all wait until the very last moment to jump off back into the water, for this reason I have to go slow so no one accidentally jump out of the tank.
My Black ghost likes to do what your betta does, he winds up curling against my arm and palm. He is a bit big (16 inches) to fit very well, he is hand fed, has been ever since he was a baby. He gets an attitude though if I mess with his lair(Prune plants, vacuum around it, or tidy up the substrate as the Geos mound it up in odd places). Holy smokes.
My red hump Geo and one of my electric blue acara show off to each other. They do the shimmy, mouths open and do a bit of flashing. They follow each other everywhere. It is strange but they never nip or act agressively. They are an odd couple.