I would suggest getting a hydrometer to see check the SG
of the water you're putting in.
I use Nutri Seawater myself. My LFS
sells it for $12.50 for 4.4 gallons. I live in a condo, so its just worth it for me and real easy to handle.
I am just anal, but I test every new jug of water I buy for SG
and ph. Just to make sure I didn't get a crazy batch or something. So far, I am on my 5th jug, and its all been consistent.
1.019 is ok, just on the low side of ok IMO
. If you plan on adding inverts, you probably should bring it up to 1.022 or so. So, you may just want to top it off with saltwater for a week, checking SG
every other day, or do a 10% PWC
and see where your at. You should be perfect then. You are already off to an amazing start!! Beautiful tank!!