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President Trump announced in a press conference Thursday that chloroquine phosphate -- a substance found in drugs used to treat malaria and severe arthritis -- was cleared by the Food and Drug Administration (FDA) to test as a treatment for the coronavirus.

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That same substance, outside its pharmaceutical form, is used as an additive in aquariums to kill microscopic organisms that might harm fish and other aquatic animals. And, the prices for chloroquine phosphate have surged online in late February and early March, according to a study published Thursday, sparking fears that people may be ingesting the fish-tank additive in the hope it will combat COVID-19 illnesses.

The study, conducted by Storyful before Trump named the drug publicly Thursday, analyzed three identical listings from the same eBay seller, “thechemicalsource,” who opened bids on bottles of chloroquine phosphate used in aquariums for one week. Between February 25 and March 2, the price paid for a single 25-gram bottle of chloroquine phosphate skyrocketed from $9.99 to more than $500, the study said. The seller warned in each listing that the substance was not for human consumption.

Speaking at the same press conference with Trump, FDA Commissioner Dr. Stephen Hahn said chloroquine phosphate will be used in clinical trials to test its effectiveness in treating COVID-19 but also warned about providing the public with “false hope.”

"We will collect that data and make the absolute right decisions based upon those data about the safety and efficacy of the treatments,” Hahn said.

“What’s also important is not to provide false hope," he added. "We may have the right drug, but it might not be in the appropriate dosage form right now, and it might do more harm than good.”

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Several countries reported in recent weeks that the drug was helpful in treating COVID-19 illnesses but there have been no conclusive pharmaceutical studies to back up the claims. The World Health Organization (WHO) has chloroquine phosphate listed as an essential medicine for its treatment of malaria but has not approved the drug for treating those infected by the coronavirus.