Marble crayfish aka Marmorkrebs are self cloning craysfish that are mainly used for feeding the cray fry to fish to get them into breeding condition.
They make interesting pets, and can also turn blue by being fed spirulina.
Looking to trade for shrimp. Just about any shrimp. Hit me up with an offer. I have adults and babies. PM me.
I stay around 10 for a 5.5 x 8 breather bag. Some do more. It's really what you are comfortable with. Be sure to add moss or a sponge for them to grab onto, and if using a breather- don't leave any air in the bag.
My wife and I don't buy anything for each other either. It all goes to the kids. She and I buy stuff for ourselves off and on throughout the year anyway.