(CNN) A Phoenix-area man is dead and his wife is under critical care after the two took chloroquine phosphate in an apparent attempt to self-medicate for the novel coronavirus, according to hospital system Banner Health.

It does not appear they took the pharmaceutical version of the drug, but rather "an additive commonly used at aquariums to clean fish tanks," Banner Health said in a statement.

Though Banner did not provide additional details, NBC News spoke to the wife, who said they learned of chloroquine's connection to coronavirus during a President Donald Trump news conference, which "was on a lot actually." They took it because they "were afraid of getting sick," she said.

"I had (the substance) in the house because I used to have koi fish," she told the network . "I saw it sitting on the back shelf and thought, 'Hey, isn't that the stuff they're talking about on TV?'"

Trump has touted chloroquine as a possible treatment for Covid-19. It is approved by the Food and Drug Administration for treating malaria, lupus and rheumatoid arthritis, but the FDA has not approved it to treat the coronavirus.