Can't Get My Salinity High Enough


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I'm using Oceanic salt mix. I bought a jug that is supposed to make 50 gallons.

I have a 30g tank, and I've got some crushed coral and sand in the tank--so you'd think I need to make up about 27g +/-. My refugium holds about 4 gallons. So maybe 31-35 gallons at best. I'd say that it sounds reasonable to expect I'll need to use about 1/2--5/8 the jug of salt mix +/- to make up enough for my tank. I've measured out what the directions indicate and I'm WAY low on salinity. Used right about 5/8---3/4 of that jug of salt mix. Seams I'm on track--if you believe the directions on the label.

My salinity is only about 1.015 :frustrat:

I've had this thing pumping and churning for a couple weeks now. I'm using the glass floating hydrometer--the one that looks like a thermometer with the tall skinny neck on top and all the graduated marks-- with the green spot in the middle between 1.020 and 1.026.

In order for me to get my salinity up to 1.019 or 1.021 -- I'll have to use another 1/2 of what I got left. :frustrat:

So whats the deal?
Is this REALLY a 35 or 38 gallon jug mix of salt and the manufacturers are sticking it to me with marketing hype or false advertisement?

Or do I have a problem?

Don't remember this happening 20yrs ago when I was a kid. I followed the directions and when I bought a 50 gallon bag of salt mix--it made about 50 gallons of salt water. I know, because I used to change about 50 gallons of SW every couple weeks and I'd just dump that whole bag in my 50g plastic drum, add water and turn on the powerhead for a couple days. I always checked it before adding it to my tanks and darned if it wasn't usually between 1.019 and 1.021.

Seams to me that I've used enough salt mix to make up about 40 gallons of SW from this new Oceanic jug and I'm not seeing the results I expected with my hydrometer.

WTF is going on? :frustrat:

Bad hydrometer? Seams a stretch with a glass hydrometer, but I guess it's possible.

Given my paranoid and distrustful opinion of big corporations--I suspect the salt mix. :shock:

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I'd have the LFS test it before I blamed the salt.
I have yet to see a hydrometer thats accurate.
I would try a different hydrometer which BTW is a good idea.I keep two different brand hydrometers on hand.Hydrometers are temperature specific,1.024 at 78 degrees is ideal.A more accurate device is a refractometer.Sorry,I never had a salt mix that wasn't close to what it states.
yeah, reeffreak has a good point. get a different hydrometer. I have had one test different three different levels of specific gravity in three different areas of my tank. It was like .019, .023. and .028. Needless to say, I tossed it and got another one. Good Luck

-Dr Marco :sfish:
I've heard of seasoning the plastic hydrometers, but this is a floating glass hydrometer. You can't season that--or can you?

I'll try a different hydrometer.

My temp is 76F.

Nope, floating glass hydrometers are much more accurate than the plastic arm ones. We use floating glass ones in my lab at work.
Fill up a container with R/O water and float your hydrometer in it. you should read 1. if not write down the correction and apply it for your saltwater tests. The calibration test with the R/O water should be same temperature as the salt water to be tested. hope this helps.