Q's about darts in general.

[Mentat]

...should i use a heater under the tank for humidity for my Azureus? my house is usually about 70 f winter or summer, and i will be misting a few times daily. and if i use a heater will it bother the springtails?

D tinctorius Azureus prefer temps in low to mid 70's and can tolerate down to 65F. Long exposure to high temps above 80F can be dangerous. You do not need any heat source; specially one under the substrate which is a no-no for frogs.

Humidity is maintained by manual misting (I do twice a day) or with the use of misters/foggers controlled by timers or automatic controllers .