The tank doesn't release muscle tension. Because you are fully supported, you don't need to contract an muscles to maintain your posture/position, so basically you can relax all of your muscles at the same time. In my opinion, its just a gimmick, you could get the same effect from lying on your bed and relaxing all your muscles through using deep breathing exercises(like meditation).
Sensory deprivation, surely eye masks(the things you get on aeroplanes) and earplugs would deprive you of any sight or sound stimulus.
Want good skin, drink lots of water and if you want the immersion tank solution, add a couple of spoonfuls of salt to your bath, or add lavender and tea-tree oil which are just as good if not better for your skin.
The induced current is just a gimmick, and whatever some people say, it won't remove extra toxins from your body.
No offense guys, but its another one of those gimmicks to get you to waste/spend your dollar.