I've had mine survive with 4 weeks with no filter. I only added a filter because the water got murky as all get out. And they survive fine without a heater. Mine are currently surviving, thriving and breeding at 68 degrees. There's no reason your tank should dip to 50 degrees at night unless its outside. My tank is right next to a window and it's been in the 20s here and the tank dips to 66 on those nights.