is my Sg too low to start a reef?
 

My 90 gallon has been set up for 2 months now and I want to add coral but my refractometer keeps giving me salinity readings of around 1.020 to 1.021 only. Is this going to be too low for most coral? How do I go about gradually raising the Sg without harming my fish? thanks

Yes, raise to 1.025 by topping off w/ salt water.

Thanks for the advice. I actually started doing this today,...should I let my maxi jet mix in salt for a gallon or some other small amount for the standard 24 hours or does it matter?

also when doing your water changes you would use replacement water with a slightly higher SG.

I would just stir salt w/ a spoon and add--no need to wait.

Excellent, thanks.

why would you do that?

When water evaporated, in main tank, that automatically raised your SG level

Yes but you have to add more water in there to top it off. If you add fresh water the salinity will get lowered back down, thats why you have to top off with saltwater then.