Saltwater Mixing Issue

[Audfish]

I use Instant Ocean for my water. When I follow the directions on the package (I even level off the measuring cups) the salinity is always lower than it should be (1.021 instead of 1.023) I airate the water with an airstone and I keep the house at 75degrees (same temp as tank) The pH is also low (probably because of the low salinity) Is there something I'm doing wrong or is the package inacurate? Has anyone else had this problem?

 

[Ter]

what are you using to measure the specific gravity? a swing arm? if so they are sorta self correcting when it comes to temperature.. Whats the PH? a stable PH is better so 8.0 can be fine, even lower sometimes.... how much water are you making? you might want to use a powerhead, airstones are good for nothing ( I say )$...
Ter

 

[andywg]

The moment you open the salt packaging the salt inside will start absorbing moisture from the air. As such any "cups/gallon" mixing recipe will become more and more inaccurate over time through containing more water and less salt.

This is why you should always use a refractometer or hydrometer when mixing salt.

 

[sophos9]

:stupid:

What are you using to measure? The measures on the pack are guidelines... Use your target and weigh how much salt it takes to get there, there will be some variability but you will be a lot closer

 

[Audfish]

I just use some measuring cups that I bought specifically for the aquarium. However, andywg seems to have a valid point. I only make 4.5 gallons at a time so the salt has been open fora while. I do use a hydrometer to measure so I've just been adding a tablespoon or two until the sg gets to 1.023.

 

[andywg]

I do use a hydrometer to measure so I've just been adding a tablespoon or two until the sg gets to 1.023.

Best way to do it