Black Skirt Tetra not well
When you have issues like this, true best thing is to do a large water change, ASAP! As much as you can while still leaving 1-2" for the fish. Then refill and double dose water conditioner.
Unfortunately I don't think your tetra will make it. In my 8 years of Fishkeeping, if a fish is swimming sideways/upside down and has an infection of some kind, it rarely will make it much longer.
Best thing is prevention by keeping up with your water changes and keeping your water parameters in check.
Btw I'd set the water temperature to 76, 82 is pretty high!
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