how big do they get and how big of a tank do they need and what do they eat?

Uromastyx have several different species that range in size from 9 inches to 3 feet. so cage size varies for the most commonly kept species i'd say around 60-gallon long or breeder my midgit of a mali is in a 55 long and my saharan in in a 6x2x2 enclouser and will have a mate living with him when I can afford all the vet checks new quarentine lights and such. they need basking tempertures from 110-130 degrees , they must have a UVB light I use 8.0s on my cages.
substrates debatable but they should be able to dig. They are vegetarians and eat dark leafy greens, collards,mustard,dandelion ect. and some vegetables I usually give mine squash. they eat very little fruit if any, at least mine dont like it and it gets nasty quikly in the heat.
common health promblems are tailrot, respritory promblems,& hyperkeritotic dermitisis ( a crust around the mouth).
i dont think their for beginners although others do
i have more information I just can remember the exact names of some things so i'll get back to you

You can also feed them crickets. But 97 percent of the food they eat should be veggies and greens.

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The more you whine, the worse it will get.

I've found that juvies grow fast.But when they reach about 1 1/2 yrs old their growth rate slows down dramatically.I have a couple that are about 4 yrs old(Mali's)and the male is only about 13 inches long.

but a 60 gallon long I might not getting one for a LONG time it's hard just getting 20 bucks for doing chores and I still need stuff for my other guys my two leopad geckos can't be house together the one bit the other I still need a uvb light thingy and a HOOD lol yea I ran out of them lol lol lol lol too bad so that's 20 bucks their then a 60 gallon is hard to come by for me is a 40 gallon breeder fine?I know where I can them.Should I use heat rock or basking lamp (I have both) I have a under tank heater too veggies can be bought every Sunday in out family shopping (I pay for the stuff they need everyone else pays for food)and what shouuld I use as subtrate?sand?I need to do some reading (there's something I'm good at )

and I went to a show and I think I saw some uros and they had this cool looking one witha tail that spread out at the end at was all pointy and he was all green with some black he was cool I'll look for some pic to show you for you can help with id of him

I have my Mali's each set up each in a 36" long enclosure and it seems to be working great.You won't need the heat rock.If you place a piece of rock or slate under the heat lamp for them to bask on, it will get sufficiently hot on its own.