So i bought a Zilla heat mat that was intended for a 10-20 gallon tank a few days ago and i plugged it in and everything seemed fine but it started making strange noises. So i took it back the next day and exchanged it with another new one and the strange noise persisted. Is this normal? I had the mat and a ceramic bulb plugged into 1 outlet. So I experimented and plugged my ceramic 100W bulb into a surge protector (in the same outlet), and then plugged the mat straight into the outlet (not in the surge protector, but in the same outlet). The noise was reduced significantly but it still happens. what is the problem here?