Not sure if that's relevant.

Once a drug is approved by the FDA for one disease, it can be used off-label for other purposes.

It absolutely is relevant. A layperson will hear "chloroquine works on Covid-19. The FDA's approved it. The President himself said so."

Like I could go and say "The FDA has approved Rogaine." It's true, but it's a useless statement in the context of Covid-19.

Iodine is approved for treating exposure to radiation. That doesn't mean it's OK to start drinking from a bottle of industrial-use iodine that isn't made for human consumption.

Likely much safer than taking aquarium cleaner, presuming correct dosage. These things tend to be chemically pure.