[Travis L. Stevens]

Definitely get a heater, but since you're just cycling and there is no ornamental livestock in there yet, it isn't a pressing issue. The bacteria that are helping your tank through the Nitrogen Cycle are not very picky on temperature. On the other hand, some of the hidden life might be. Any snails, crabs, forams, etc that might have came in on your rock may enjoy some slightly warmer temperatures. When adding the heater, make sure to heat your water back up over the course of a few days as to not shock anything in the system.