Dojos are a coldwater fish. While they will certainly live in temperatures above 70F, over the long-haul, it will shorten their lives if they are continually kept in water that warm or warmer.
Anything constantly above 70 really isn't good for them, though they will tolerate it. If you want your dojos to live out the full span of their normal life, which is several years, you should keep them in cooler water. Sixty-to-70 degrees fahrenheit is good.
-- bigmamafish