Reef tank temp - stable as possible or allow to fluctuate?

[Fisherman Joe]

Hi all.
Recently installed a UV steriliser and pump in the system

My temp was 26C (78.8f) and it’s now 27C (80.6f).

Is it better to set the heater to 27C or let it sink back to 26C and ramp up to 27 during the day?

 

[Jekyl]

Mine fluctuates between 77 and 78 regularly

 

[Fisherman Joe]

Does the reef temp fluctuate? That would be interesting to know.

 

[I never finish anythi]

Mine goes between 76 and 78 all seems well

 

[ISpeakForTheSeas]

Does the reef temp fluctuate? That would be interesting to know.

Slightly diurnally and seasonally, yes:
"The diurnal temperature variations are about 0.3°C in theopen oceans and 2 to 3°C in shallow waters."
Source: https://www.academia.edu/36838790/Chemical_Oceanography
From what I've seen, for most tropical reef organisms, as long as the temp doesn't swing too far too fast, and as long as the temp is kept within ~75-82F (lower than 74ish can start causing problems, higher than 83 and many corals will start to bleach - so allowing for temp variation due to imperfect temp controllers in our tanks, I would set 75F as the min and 82F as the max), the temp doesn't seem to matter much. To give an idea, a 2C change (from 25C to 27C, for example) is about a 3.5F change (77 to 80.6, with the 25C to 27C example), so allowing a 3F to 4F temp change diurnally should be fine.

 

[Fisherman Joe]

Slightly diurnally and seasonally, yes:
"The diurnal temperature variations are about 0.3°C in theopen oceans and 2 to 3°C in shallow waters."
Source: https://www.academia.edu/36838790/Chemical_Oceanography
From what I've seen, for most tropical reef organisms, as long as the temp doesn't swing too far too fast, and as long as the temp is kept within ~75-82F (lower than 74ish can start causing problems, higher than 83 and many corals will start to bleach - so allowing for temp variation due to imperfect temp controllers in our tanks, I would set 75F as the min and 82F as the max), the temp doesn't seem to matter much. To give an idea, a 2C change (from 25C to 27C, for example) is about a 3.5F change (77 to 80.6, with the 25C to 27C example), so allowing a 3F to 4F temp change diurnally should be fine.

Very comprehensive answer. Exactly what I wanted. Thank you.