Hi! I’ve had the Aqueon Submersible Aquarium Heater 50W in my 5 gallon tank for 3 days. I followed the instructions on the packaging when I first got it but all of today the light has been flickering, turning on steadily, flickering, turning off, and repeat which I was led to believe shouldn’t happen and instead it should go from off to on no flickering in between. The temperature in the tank goes from 77 F - 80 F. There isn’t a fish in the tank as of right now but before I get a fish should I switch heaters? I got this heater off of Amazon which I think might be where I went wrong but the store closest to me sells Aqueon Pro heaters would they be better/safer?