How should I introduce new toads to my enclosure?

[Amber Gyore]

I have a 20g viv, and want 5-6 toads. I was just wondering if there was anything special I should do to introduce them. I was hoping that maybe having a higher population will encourage the two I have now to lighten up a bit. Their colour changes have been closely monitored, and I have experimented with everything including air temperature, water temperature, substrate, various decorations, lighting (UVB Vs reg, and different watts). I'm thinking more company is the last thing I haven't tried. Plus I love watching these guys jump around, so I figure the more the merrier.

[Pezoneden]

4-5 in a 20gal should be nice