Join Date: Feb 2012
Location: Ontario, Canada
My fire red tank gets to as low as 60F, it's okay. Although your room temp is 50-76 but the temperature in a 10G tank won't fluctuate as much, likely will be 60-65 range. My fire reds still breed and babies are okay too, they grow/breed much slower than when the temp was 74 in the summer though.
No filter will be a bigger problem though, the ammonia/nitrite and to a lesser extend, nitrate, will eventually kill them. Even if they don't get killed, permanent damage can be caused if they stay in that environment for too long.