How does low temperature & temp flux affect plants

[Rofellos]

I've recently started a small nano tank (using one of those plastic creature-keeper type tanks) prob. around 3 gals. I'm trying to keep costs low and currently am using a 24watt regular screw in CF bulb and plan to add diy CO2 through a red sea filter.

I don't have the money to spend on a heater (and I've read mixed reviews about the nano heaters too...) and was wondering how this would affect plant growth? With the light on the water gets to around 71 deg f and with the light off it dips to 60 deg at night.

I currently have some glosso and few stems of rotala in there, and was planning to add riccia later on.

Thank you for your help in advance.

* btw are there any shrimp that would survive in that temp range?