ya no top offs, combined with doing water changes and topping off then is whats made your sg
go up. I'd just take out a bit of water and add freshwater...let it be for a while, then if its still too high, do it again.
But i'd suggest using RO
water, and not using tap. Tap water will have nitrates and phosphates in it more often than not, and the water conditioners dont do anything for that. Since you dont have an RO
unit, i'd just go to either a water store like watermart, water and ice, or go to your lfs
(they usually have it) or even walmart and get RO
water. Tap is often the cause for algae cuz of the nitrates and phosphates.