I keep a data base on my laptop. I track feeding, weights, sheds, + all life records I.e hatch date, purchase date, amount paid, vet visits, sold when, how much. I don't log in when they poop. I use a grease pencil and the poop date gets marked on the tub. Animals that are sold get there records moved to another folder and saved. I have a file backed up on every animal that has been in my possession since I started keeping more than just a couple snakes in 2009. When I sell an animal I ask if the new owner wants a copy and print it out for them. You would be surprised at how many people say no thanks but I never delete them incase they call at a later date with a problem or want the records.