I know that kale is ready to be eatan but do they have any bad effects on the tortoise

HI

Kale is Ok to give sparingly to bulk up the weeds. It is an oxulate which inhibits the intake of calcium, but a bit won't hurt. If you are finding it hard to get any weeds, you could also bulk up with Florette salad, sold at most supermarkets, just make sure you give it a good wash first. If you go to the link below, they will tell you what is available for picking at each time of the month.
http://www.thetortoisetable.org.uk/site/tortoise_home_1.asp

HTH
Jane