"A man has died and his wife is under critical care after the couple, both in their 60s, ingested chloroquine phosphate, an additive commonly used at aquariums to clean fish tanks," which is also part of one of the antimalaria drugs that President Trump has mentioned in recent days, according to Banner Health, the hospital system that treated both patients.

Why it matters: People who attempt to self-medicate risk serious side effects or death, and it's why any messaging about chloroquine and the related hydroxychloroquine should emphasize that these drugs have not been approved to prevent or treat the new coronavirus.

Worth noting: The malaria drug comes in tablet form, but the type the couple used was a toxic substance — not medication.

The man's wife told NBC News: "I had it in the house because I used to have koi fish."

Go deeper: Trump touts drugs not yet approved by FDA for treating coronavirus

Editor's note: The story and headline have been corrected to reflect the fact that the form of chloroquine the couple ingested was used in aquariums (not the medication).