Problem with your Jellyfish? Undissolved salts could be the culprit.
The other most common problem concerning salt levels in your jellyfish aquarium, besides inaccurate hydrometers giving a false reading, is how the saltwater is made. Undissolved salts can also give you an inaccurate reading which is a problem since jellies are very sensitive to salinity changes & high salinity levels can also impede their movement, eating and overall cellular activity. It is important to know what your salinity is and how it changes over time.
The point I need to make here is about how you make up your saltwater distilled or RO water.
Always prepare the saltwater at least 24 hours ahead of time. Adding undissolved salts to your jellyfish aquarium will damage the jellies tissue and can cause them to be very still and not bell or pulse much…their bell can curl under and they will fully retract their tentacles and not eat because of the tentacle retraction. They will look and be sad….sad jellies. Also a dusty film of white on the interior of your tank will form, which can make the tank look cloudy.
Properly aerating saltwater involves a small submersible pump called a powerhead, and a bucket. A simple "bubble wand" or "bubbler" will not degauss and dissolve the salts completely. I know the words "aeration" and "bubbler" tend to go hand in hand, but in this case it's just not the right tool for the job. You need more mixing power in the water which a powerhead can give you. Once you add the desired amount of salt, vigorously mix for a minute or two with your hand or 2 foot length of PVC pipe as a stir stick. After that, you can let the powerhead pump ( in this scenario a Lifegard 800 is perfect!) do the rest. See diagram above to see how to set this up in a 5 gallon bucket. It could be any size bucket as long as you position the powerhead pump at the water level allowing it to pull in air as it mixes. You want the water and air to be churning vigorously.
If you have some residual stuff still swirling around the bottom of the bucket after 24 hours don't worry about it. Just leave it there and don't try and mix it into the water you will be using for a water change. You can rinse that out and get rid of it before making another batch of saltwater. It's just undissolved minerals and is totally normal.
Important Side Note!!
Never use tap water to make up your saltwater--not even if you use some sort of water conditioner that removes chlorine. There are heavy metals, pesticides and ever more increasing levels of pharmaceuticals in city tap water supplies. No sort of chemical conditioner will eliminate these things from the water. You must use distilled or RO (reverse osmosis) water. Do not use "spring water" or "mineral water" or "drinking water" --- it must say "Distilled" or if you are purchasing from a water store, it must be RO or RO/DI.