For some Olympic athletes, Rio officials’ attempts to fix the green pool water at the Maria Lenk Aquatic Center has only caused more problems.

“I could barely open my eyes for the final quarter,” Team USA men’s water polo captain Tony Azevedo told reporters after their 6-3 victory over France on Wednesday. “This is the Olympic Games and they are putting so much chlorine in the water that people can’t see. You can’t have that.”

Hungary’s Gergo Zalanki agreed.

“My eyes hurt from the water, it’s not good,” he said after his game against Greece on Wednesday that ended in an 8-8 draw. “It feels like they added more chlorine to the water but I’m not sure. I’m used to it because we have a lot of water like this in Hungary, but I think there might be something else wrong too.”

Rio Olympics officials, however, maintain the chemistry of the pool, including the chlorine levels “are within the required standards.”

“We have treated both pools during the night [on Tuesday] and the alkalinity levels have already improved,” Rio Olympic spokesman Mario Andrada said at a press conference on Wednesday. “We expect the color to be back to blue very shortly.”

In the meantime, he said, “there’s absolutely no risk, no effect for athletes who will compete in the pool.”

The diving pool, the smaller of the two pools at the Maria Lenk Aquatic Center, turned green on Tuesday due to “a proliferation of algae” caused by the lack of wind, hot temperatures and ongoing rain, according to Andrada. By Wednesday, the pool used for water polo and synchronized swimming also began to lose its normally crystal-clear blue hue in favor of murky green.

Andrada said “a sudden decrease in the alkalinity” caused the bloom, but that treating the water had already begun to remedy that by Wednesday morning. Andrada didn’t specify what treatments Olympic officials used, but it’s common to use chlorine to eliminate algae in pools, according to Erica Andresen, who works as the associate director for George Mason recreation facilities, which operates an indoor Olympic-sized competition pool.

Andresen said she’s never seen anything like what’s happened in Rio and postulated that officials likely “shocked the pool,” or used high amounts of chlorine, to fight their algae issue.

“They probably super-chlorinated it,” Andresen said, noting that if officials didn’t allow the water to run through the pool’s filtration system enough times, swimmers could experience symptoms like burning eyes.

“They may have over-chlorinated that pool,” she said.

If so, athletes say, that’s now the bigger problem than the pool’s color.

“What’s ridiculous is not the green water. I’ve played in plenty of pools with green water,” said Azevedo, who’s hoping to win Team USA’s first men’s water polo gold medal this summer. “Who cares about the green water? The water could be any color, it doesn’t matter. What matters is that it’s safe for us.”

Rick Maese contributed to this report.