Originally Posted by tecwzrd
Originally Posted by produceb
I put a heater in at 78 it just got even hotter in the evening over 80.
That's due to a heater problem, the internal thermostat didn't maintain the 78 degrees during the night. Either that or it was hotter at night then during the day which happens sometimes also
See... that's what's eating at me. It's not necessarily a heater problem... it's just that the lights are pumping heat into warmer water to start with, and you'll therefore end up with even hotter water. My bet is that if you set your heaters to 80 degrees, at the end of the next day you'll end up with 82 degree water. By the "highest temperature" logic, you'd set your heater now to 82 degrees. At the end of the next day, you'd be at 84 degrees... because the heat from the lights has the capacity to increase water temperature by 2 degrees - regardless of what temperature it started at.
Now... getting really picky here - there is a theoretical problem with my thinking because the heat capacity of water is not constant - it changes depending on temperatures. So basically... given a set heat energy input, really really hot water will not increase in temp as much as really really cold water. But for the temperature ranges we're talking about for our tanks, this really doesn't come in to play.
Assuming room temps stay constant, and heater thermostats are perfect, it just seems like for a given light over a given tank, you have a given amount of heat energy to dissapate. If you don't use fans, that is going to dissapate into your tank, thus raising the temperature. And it just seems like that energy doesn't give a darn about the temperature of the water.
Can you tell I'm still not convinced!