I don't have much support for using Epsom salt. Many aquarists add Epsom salts (magnesium sulfate) to the aquarium’s water – do not do this in marine aquariums, its use is primarily as a tonic/dip for freshwater fish. Seawater formulas already contain between 7 and 19 grams of magnesium sulfate per gallon (depending on the recipe). NSW magnesium level is around 1200 ppm and sulfur is around 840 ppm. Epsom salts do have some possible benefit when mixed into the food as a 3% by weight adjunct. Some benefit might be achieved using it as a dip in additional concentrations, but adding a small amount to a marine aquarium itself has no benefit. All the above is regarding fish with constipation.
A
video longer than one minute under white light up close to the fish, showing both sides of the fish would be helpful. You can upload the video to YouTube then post the link to it here. Otherwise, I have to assume you have done the correct diagnosis -- a swim bladder issue.
If you have a Rhomboid Fairy Wrasse (
Cirrhilabrus rhomboidalis) then I can say it needs to be in a 90 gallon or larger aquarium. They are sometimes collected as deep as 130 feet. If they are caught at that depth they need to be slowly brought to the surface, otherwise they may have buoyancy problems that can express a few days to a couple of weeks later, that is, a decompression issue. Another decompression issue can arise in an air flight. Cargo holds are sometimes poorly pressurized. The treatment is to remove the excess air using a syringe. But still, no guarantees for success. In fact I've not seen this work effectively when done. It removes the gas but not the cause.
Many aquarists
think their fish has a swim bladder issue, when in fact it is gas in the digestive track. This is brought on by feeding pellets and/or flakes. This is mostly a wait-and-see remedy.
Lastly, there are gas bladder issues that occur for some unknown reason. No way to treat this.
---------------
Some fish can live a long life with a buoyancy problem, so long as they keep eating. As you can see from the above -- not much you can do.