Healthilly, only up until the first time it uses the bathroom, or the first time you feed it, and ammonia enters the tank. Even if you clean it it wont be healthy, you could do a dangerouse, stressful full water change. Or you could change part of the bowl water and leave the rest of the toxins.
You MUST have a filter!. Get the biggist bin you can find at wallmart or target, or your attic, and add a filter.