couple questions

[thefishguy]

what is the max flucuation of the temperature. mine goes from 78.5F-81.0F. Same for the SG what is the acceptable range. Also I have question about ph. How do I regulate and keep it from flucuating.

 

[hcuellart]

I would say 2°F max deviation in temperature. As for SG, there should be no variance, at the most .001 0/00 per day. pH fluctuates naturally from respiration processes so at day your pH would be higher than at night. Ideally pH should be around 8.2-8.3 at midday. If your pH is fluctuating by more than .2 then you might have an alkalinity problem (low).
Alkalinity measures the buffering capacity the water has (this is a quite simple explanation there is much more to it) so if you do not have an alkalinity test kit buy one and try and have your alk anywhere from 8-12°dKH the upper limit being for a reef tank.

Good luck.
HTH