Magnesium Bath Soak Overview Higher Dose Serotonin Soak is a mineral-rich magnesium bath soak crafted to melt away stress, soothe sore muscles, and transform your bathtub into a full-body spa ritual. Formulated with pure Zechstein magnesium flakes, apple cider vinegar, skin-softening algae, French green clay, and seaweed, this luxurious d