A possible reason for the toads venturing into the water more before because the land was possibly to dry or not giving them much for what they required. Unless an animal is known to be fully aquatic, many amphibs venture onto land and water equally.

Possible water temp might have something to do with it too, I noticed them use water more when the water was in the higher 70's and very low 80's.

I would not recommend keeping the two type of animals together.