FAQ How do I mix ocean water?

Special credit thanks to Wendy at Hermit Crabs R Us for compiling and sharing this list!!

After mixing all ocean/sea mixes leave sit for at least 12-24 hours prior to offering to ensure that all the crystals have dissolved.

Ocean or Marine salt is required by hermit crabs

Ocean or Marine salt is required by hermit crabs

Crystal Sea Marine mix Bioassy Formula
The site from which I purchased this mix indicates 1/4 lb or 1/3 cup will yield 1 gallon. I found it to only be 1.016 SG when mixed this way. I tested it using 2 different hydrometers-one that was also purchased at the same site as the salt mix. I mixed it using 1/2 cup and got 1.021. (I add an additional tablespoon for my C. Perlatus to raise it 1.023)
* 1 1/2 tsp per 8 oz (1 cup) water
* 1 TBSP per 16 oz (1 pint)
* 2 TBSP per 32 oz (1 quart)
* 4 TBSP per 64 oz (1/2 gallon)
* 8 TBSP per 128 oz (1 gallon)

Instant Ocean
The package indicates to use 1/2 cup (which=8 TBSP) per gallon.
* 1 1/2 tsp per 8 oz (1 cup) water
* 1 TBSP per 16 oz (1 pint)
* 2 TBSP per 32 oz (1 quart)
* 4 TBSP per 64 oz (1/2 gallon)
* 8 TBSP per 128 oz (1 gallon)

Oceanic Natural Sea Salt Mix
The package to make 5 gallons indicates .29 lbs/gallon. I measured the package and it was approximately 2 1/2 cups. Which is 1/2 cup per gallon or 8 TBSP
* 1 1/2 tsp per 8 oz (1 cup) water
* 1 TBSP per 16 oz (1 pint)
* 2 TBSP per 32 oz (1 quart)
* 4 TBSP per 64 oz (1/2 gallon)
* 8 TBSP per 128 oz (1 gallon)

* This is the salt I am currently using and 8 TBSP makes a specific gravity of 1.021. I use an additional tablespoon to raise the specific gravity for my C. Perlatus. I also provide Doc Wellfish crystals in the food dish as well.

Red Sea Salt
The package directions indicate 2.8 lbs. dissolved in 10 US gallons, which is .28 lbs for 1 lb which again is basically the same as Oceanic 1/2 cup per gallon (or 8 TBSP)
* 1 1/2 tsp per 8 oz (1 cup) water
* 1 TBSP per 16 oz (1 pint)
* 2 TBSP per 32 oz (1 quart)
* 4 TBSP per 64 oz (1/2 gallon)
* 8 TBSP per 128 oz (1 gallon)

Tropic Marin Sea Salt
The package instructions indicate 151 grams = 1 gallon. 151gms x .0353 = 5.33 ounces.
5.33oz/8(oz in a cup) = .66 or 2/3 cup per gallon. There are 31.68 or 32 tsp in 2/3 of a cup.
* 2 tsp per 8 oz (1 cup) water
* 4 tsp ( 1TBSP+1tsp) per 16 oz (1 pint)
* 8 tsp ( 2TBSP+2tsp) per 32 oz (1 quart)
* 16 tsp ( 5TBSP+1tsp) per 64 oz (1/2 gallon)
* 32 tsp (10TBSP+2tsp) per 128 oz (1 gallon)

So basically all of the dry salt mixes tend to be 1/2 cup or 8 TBSP per gallon of water. If you are unsure if your sea water is salty enough or too salty you can purchase a hydrometer which measures specific gravity. The specific gravity of sea water varies depending on location, but is generally somewhere between 1.020 and 1.025. To get an accurate result with your hygrometer, the water should be around 77 degrees Fahrenheit.
If you are offering both a de-chlorinated fresh water dish as well as a de-chlorinated salt water dish, you needn’t worry if the mix is too salty. The crabs can adjust their shell water accordingly. If you have C. Perlatus, saltier water is more beneficial as their shell water has been shown to be much higher in salt content than those of other species.
In addition, if the salt water dish is not salty enough, they will need to obtain natural sea salt from other sources such as their diet. One option is to provide a small pile of the Sea salt crystals with their food.
Here is some additional reading about specific gravity (versus salinity)

Saltwater Salinity and Specific Gravity


* CUP tsp TBSP
* ¼————–12——–4
* ½————–24——–8
* 1————–48——–16
* 2————–96——–32

* How many ounces in a:
* 8 cup
* 16 pint
* 32 quart
* 64 1/2 gallon
* 128 Gallon

Conversion Table

Additional information added to Wendy’s compiled Ocean mix, by Marie (aka ladybug15057)

Both the ZooMed Part 2 and HBH hermit crab salt mixes were tested for salinity levels. If mixed per the products instructions, they do not register a salinity level on a hydrometer. Land hermit crabs should be offered an ocean/sea water pond with a salinity level of 1.021-1.024.
ZooMed Part 2 has a yellow dye within it, something a hermit crab does not need within their diet. Within this product, it does not contain an ingredient to remove heavy metals from tap water, as well as ZooMed Part 1 fresh water conditioner does not contain a heavy metal neutralizer.
HBH Hermit crab sea salt Ingredients: sodium chloride, magnesium chloride, calcium chloride, potassium chloride, potassium iodide
It contains the wrong form of calcium and it contains normal table salt ingredients sodium chloride/ potassium iodide. HBH salt mix also contains a highly corrosive magnesium chloride that is used to stabilize the iodine. (Thanks to SUE, RFCrabs for this information regarding HBH salt mix)
It is not known for fact whether either of these Salt mixes for hermit crabs are made with freshwater salt mix or ocean/sea water mix. This includes the Glub Salt water sold for hermit crabs.
Ocean/sea water elements are different than those of freshwater. Hermit crabs need the elements that are found in ocean/sea water to remain healthy:


(Please see attached file bottom right of this page)
This information regarding Epson salt was shared with Marie (aka ladybug15057) by a zoologist/biologist who is responsible for the aquarium care at a zoo in Texas.

“Freshwater” salt mixes (such as Doc Wellfishes and API) mainly consist of Epsom Salt, which is an anesthetic for invertebrates and can easily kill them. To euthanize an invertebrate is usually done by overdosing it on anesthetic where normally Epsom salt is used. An Epsom salt bath will usually cause invertebrates to slowly go to sleep.

Related Links and Archived Links:

Advanced Aquarist Salt Mixes Part 1

Advance Aquarist Salt Mixes Part 2

Salinity GPC EDU

Saltwater Salinity and Specific Gravity Algone

Why is the Ocean Salty Palomar EDU

Sea Salt Mixes- About.com