Some questions from a beginner

[Getti]

Hey! Im sortof new to this and I am looking to get some Red cherry shrimps... But I have a few questions... My dad has two tanks(a 10 gal and a 30 gal that have been up for about 10 years but right now there is only 1 fish in each. For the shrimp i am planning to take over the ten gallon one but I am not sure about the cycling process... Can I get a headstart on the cycling with the existing tanks or is there not enough bacteria because of the small amount of fish? Also I know this isn't really the forum for it but I also have recently gotten 3 red clawed crabs( about a month ago) and I did not really cycle the tank i put them in... The tank used to be a guppy tank and I still have the gravel from the guppy tank(could this help cycling at all?) And is there a way to slowly cycle a tank without killing its inhabitants? Thanks!

[Mustafa]

If fish inhabit a tank continuously there is no need to cycle a tank. As for "slowly cycling a tank with the inhabitants still in it"...well...that's already happening as we speak, but your inhabitants are being stressed by it, of course.