A heater sticking on wiped out my wonderful collection of taiwaan bee shrimp, so there is some risk either way. Depending how cold it gets indoors where you live would decide that, but you may be able to get away with not having it switched on most of the time or not really need it at all. Only if it drops below 60 would I think it really necessary! Water changes temperature much slower than the ambient temperature as well so it would have to be really cold indoors before the water dropped to match it! You may not need a heater in Oceanside SoCal I suspect?
Not sure how it’s an all new set up.
I don’t like heaters as they sometimes fail and cool the tank but I have 5 shrimp tanks in one room and the window ledge is all the room I have left for now for the smaller 6 gallon tanks
Really pleased to see you have another caridina shrimp tank. Should all fail in the other tank it would be worth redoing that tank (thoroughly clean it and don't reuse anything, that was in that tank before (equipment should be thoroughly cleaned as well), to be sure/safe) and trying again as you will hopefully have lots of spare shrimps from your good tank that you can transfer when the newly reset tank is ready. Bare in mind that it is quite common (I experienced it, even using a heater) that caridina shrimp slow/stop breeding in winter so don't panic if you don't see any/many new caridina shrimplets until next spring? Neocaridina don't seem to stop breeding any time of the year!