Hey everyone ! I just bought this heater 50watt for my 3.5 gal betta tank. Box says for “up to 13 gal tank”. Barely turned it on yesterday however, I had it in the tank for about 5 days already. Today, I noticed the heater is broken from the inside. No visible cracks on the outter tube. Can I still use it for the night? I can go to replace it tomorrow. Really weird though! Never dropped it & didn't notice anything before. Most was submerged, at least to the min point that the instructions said… Any advice would help please!