Ok and with the one that I have chosen I have some questions
1.do I need to keep it on all the time or can I just turn it on when I need it. - LEAVE IT ON ALL THE TIME, OTHERWISE YOU WON'T KNOW THERE'S A PROBLEM
2. Is there anywhere specific it needs to be placed - FAR FROM THE HEATER IS BEST
3. Can I use it in more than 1 tank or should I get 1 for each tank - ONE PER TANK IS STANDARD
4. What do I do if my heater is not putting out the right temperature it's set - ADJUST IT... TURN IT UP OR DOWN A LITTLE AND RECHECK IN A FEW HOURS.
Thanks for all your help from Tom