Quick question on salinity, its driving me nuts

My salinity no matter what i do, water changes, turning the skimmer off and adding aquarium salt seems to want to stay in the 1.016-1.018 range. Is there something I can do to get this right as i have read it has to be in the 1.022-1.025 range?
My fish are just fine and dandy, live rocks looking fine, shrimp and crabs are acting normal, the rest of the readings are coming up fine too my calcium is at 360 right now. I do NOT have corals, just fish with live rock.

ammonia 0
chlorine 0
alk 300
nitrates 20 ( just did water change)
nitrites 3.0 (again with the water change)
pH 8.4

After the water change while the equipment was turned off i cleaned everything really well, and changed the activated carbon out.
like i said the fish are acting just fine i have no idea why my salinity is just in that range, its a 90g tank, i use instant ocean, might switch it over to kent marine reef crystals as i hear this has a higher salinity

 

What are you using to test your salinity?

 

the salinity of your water depends on how much salt you use. If your salinity is that low (verify it before changing anything, maybe with your LFS) then you don't want to bring it up too fast, but you do want to bring it up. I would say no more than .02 per day...

You can mix hypersaline solutions using IO salt mix and add it in slowly when you do a WC... OR, if you are adding fresh water to top-off for evaporation, you can just top off with salt water instaed and that will bring it up fairly slowly, too.

 

like said above. get your water tested via LFS to make sure your device is right. then if you add .5 gallon or more daily for evap. just topoff with salty water and it will be where you want by the end of the week.

also for water changes, what ever the saltbrand bag instructions say..example.

1/2 cup or scoop of salt per 1 gallon of freshwater for salinity 1.023 then add like 3/4cup of salt to get something like 1.026 that mixed in with your low tank salinity will give it a raise.

 

I'm thinking you're not mixing your saltwater right to begin with...

For IO, if you want to make 5 gallons of SW at 1.026 add 3 cups of salt to 5 gallons of FW ... but...

The FW needs to be heated to around mid/upper 70's so that it can dissolve that much salt. AND you need to let it sit for at least 24 hours to get the correct SG reading. I highly recommend you let it sit with a powerhead running in the bucket for 24 hours while heated before putting that SW in your tank.

 

extra comments based on your sig

90g live rock one spot foxface, two crabs, four shrimp, two damsels

shrimp are very delicate to SG swings... if it's this tank, you may lose them, be advised.

55g DOB 3/2/10 Black reef sand
30g hexi with three oscellaris clowns, chocolate chip starfish, two peppermint shrimp, and one bi color blenny

same shrimp comment + FYI, chocoloate chip starfish are not reef safe.

 

my tank is NOT a reef tank, its just live rock i have no corals. I have been mixing it with a heater and powerhead and using three cups per five gallons as i have four five gallon buckets mixing right now and when I test them tomorrow ill post what I found on SG.
I just did a water change today on the tank, tanks been set up for a while now.
Nothing in the 55g right now except sand.
the 30g has been set up for years, all the fish in there are good. readings are normal and in check

 

and I am using two different swing arms, and a hydrometer. I have started checking into the prices of refractometers because i am wondering even after rinsing the arms after using them if theyre just not reading right due to the saltwater

 

Swing arms are notoriously inaccurate. They're rated for a large range of temperatures (typically something like 65 degrees to 85 degrees farenheit), but only actually calibrated at one temperature, for starters. Then there's the manufacturing tolerances that aren't exact, and the lack of a way to adjust them, that makes them fairly worthless.

 

Some swing arms are accurate, but I doubt the accuracy if you are having issues getting the SG where it should be.

Have the SG tested at your LFS, or a local reefers with a refractometer.