I would take a sample of your water to your store if you are just using a hydrometer because at that temp I think you'll be surprised at your actual s.g
as you can't do much about your temp they'll advise the best s.g for you.
175Ltr Aqua Marine 900, Marisys 240 Wet/Dry,
24W UV, 17.5KG Fiji Live Rock, Temp - 25C,
SG - 1.023, Amm - Nil, NitrI - Nil, NitrA - Nil,
Ph - 8.4, Alk - 4.3 Meq, Cal - 450, Mag - 1340