You really don't want them to have something to soak in because they wont soak unless something is wrong. Mites, humidity is way too low, and in some cases even worse problems are at hand. Just give you ball python enough water to last a few days in the heaviest water bowl you can find. All the caresheets say let them soak cause no one ever realizes how high the humidity should be when they are shedding. A constant 40% isn't going to cut it, 70-80% humidity when they are shedding is what they need.