Salinity ?

[Zeus2]

My sallinity is 1.020. How crucial is it to bring it up. and to what.
Alk - 11.6
phos. 0
nitrate 5
calcium 420

[CleveYank]

1.025 to 1.026 range. And if nothing is stressed or dying from the low point you are at. Do not do this in a couple days. Just walk it up nice and easy .001 to .002 per every couple days. Another way would be do not add any make up water and let it climb up slowly that way and then just mix a small batch of New Saltwater at your target when you hit it to bring sump level up to your current mark. If your sump has a high enough level that's another way to bring it up as well.

[kaskiles]

1.026
I don't know how crucial it is to raise it, but you might want to raise it gradually over a week or two with some water changes.
http://www.reefkeeping.com/issues/2004-05/rhf/index.php

[kemann]

If everything is doing well, I don't think that it is too crucial to raise it. If you are going to raise it, I agree with the above about going slowly. I guess the only trouble with having it a little lower like that would be the addition of new livestock. It seems that 1.025 is more the standard and you will have more trouble acclimatizing new things from the LFS or other reefers.