spot of iodine

So I put a spot of Iodine on my belly last night. gone this am. just rubbed it with peroxide, came back faintly. I do grind up sea veggies in my orange juice in the am. suspect im losing it in my hot tub. what can i use in my tub, that won't corrode the pump? thinking about a gallon of silver???? tub has 170 gallons. tub has ultra violet light, and water is pumped through it 24-7.