housing different breeds

Question
i have a male and female russian desert tortoise already and a friend recently gave me a male eastern box turtle.  would it be okay to house them all together?

Answer
As a general rule, I don't recommend keeping 2 different genera together that don't even reside together on the same continent in the wild. Illnesses and immunities are often pretty range specific within species and genus. But, besides that, box turtles are omnivores and need to be fed worms, insects, chicken, liver and such, as well as veggies. Russian tortoises are herbivores and need to not have access to some of the things a box turtle may eat. If they do eat it, this could cause metabolic difficulties and discomfort for them.

Though Horsfield's live in arid regions of Khasikstan, northern Iran and such, they also live in many other areas across middle Asia and southern Europe, and are not strictly "desert" tortoises. The Horsfield can handle wet or cold, but not at the same time. They can stand it colder than a box turtle would prefer, and drier than a box turtle might prefer. You could theoretically arrange a habitat that might suit their individual preferences, but it would have to be quite large, and it is better that they have separate accommodations anyway.

Another consideration against this arrangement is that your male to female ratio is wrong. If anything, you need to have more females than males. More males than females is going to cause some stress and territorial issues. Just because they are different genus does not mean the two males won't fight over the female. They may even just fight because they are different. We have a male Horsfield that butts heads with male boxies anytime they are around and tries to turn them over. Tortoises can be pretty pushy about things, and we don't keep the Horsfield with the boxies except for short periods to bathe or bask outside.

There is also a higher likelihood that they are going to harass and stress the hell out of her, being two males in there with her. Not a good idea.

http://anapsid.org/mainchelonians.html
http://boxturtlesite.info
http://russiantortoise.org