I was turning on my Aquatic Turtles infrared light at night but I really doubt that they are basking at night and it doesn't make the water any warmer so, my question is do they need the light on at night?
No. Think about if they were out in the wild at night. There wouldn't be any lights. I don't put any lights on for them at night. They will be fine without one the heater will keep the water at the desired temp.
They need mainly heat during the day that way they can dry off completely. UVB light is always a plus but where things usually go wrong is when a turtle can't thermoregulate properly because no sufficient heat source is available on their basking area.