Need hlep with temp swings!!!

I have a marineland 50w stealth and a 150w MH over my biocube(OPEN TOP) the fixture has a fan cooing the fixture down and i have a fun running at high speed in the room. IN the morning its about 72 and when the metal halide turns off its at 76.5..I have been doing this for a bit but it has not seem to affect ANY of my corals, but i have a GBTA now and im worried that it may not like that..

HEre is my idea that i thought off..RUN the heater at night only set to like 76-78. and then when i turn on the metal halide turn OFF the heater and only let the MH run throught the day. What do you guys think?

 

I think you should try running the heater at 76F around the clock and see what the max temp turns out to be at the end of the photo period.

 

Okay, does the marineland 50w shut off like when it hits the max temp?

 

If the heater is set at 76 F it should auto turn off once the water temp reaches 76 F if it does not, get another heater.

 

i have no clue if it does shut off, thats the problem. It has no light or anything on it. But thats why i was gunna shut it off like 20 mins before i turned on the MH.

 

Says it has a safety shut off.

https://www.fosterandsmithaquatics.com/product/prod_display.cfm?pcatid=21323

It should have a thermostat and function like all other heaters.

 

Okay, well i looked at the dial and its red, but it dusnt have a light to show that. idk, i guess i can just play with it.

 

I keep mine a little higher that way the lights down heat up the water as much. I keep it set at 78.9. even with the MH's 6" above the tank it raises at the most to 79.1 with no chiller. By raising the temp like you said it will be easier to keep it stable.

 

Okay, i think mine are about 5" above the water line. A fan is blowing hot air out of the fixture and the heater is set at 77. The tank is still warming up its at 73 right now.

 

Yes the was an older model heater that had the little red light to show when it was on and off. I myself like that feature, although it can be inaccurate as well.