Alm0stAwesome
Fish Aficionado
Honestly, all you need to use is put your hand in your tank and then under the tap. You want it to feel very slightly cool but not cold - you'll be able to tell Besides you can adjust it as you go. As long at you aren't pumping very warm water into the tank you won't do any harm. Even if it's too cold there's no reason to worry. I've not managed to overheat mine yet - if you see that the temperature is creeping up just change to all cold and a have a drop in temp.