I'm new to FBT's but not amphibians, so I'm excited about keeping this new (to me) species!

Last night I bought two very active little toads and put them in my 15 gallon that I'd set up for them (here's a pic/description)

I'm thinking of adding one or two more. It seems roomy enough to me but I wanted to make sure. Would 3-4 toads in here be fine?