Betta eye infection?

My poor Gweedo seems to have some kind of (bacterial?) infection on one eye. It's not popeye but just like his one eye is cloudy. He is in a 10 gallon with 2 plattys at the moment but I will be setting up a quarantine tank for him so I can start on daily water changes and hopefully prevent further issues.
Mr. Gweedo (before his eye thing)
https://scontent-a-lga.xx.fbcdn.net/...36331213_n.jpg

There are antibiotic powder you can buy from pet stores to mix into the water. They're in the fish section.

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While the antibiotics may very well help, I would try to find the root of the problem. What are your water parameters and what's your water change routine? Are there any plastic decorations he could have bumped into? I'm actually not a fan of many of the antibiotic powders they sell, good water quality is usually all you need to help it heal :). A pinch of freshwater aquarium salt could also help if you have it handy.

I'm not seeing any issues in the picture, but try doing 1tsp aquarium salt per 1 gallon of water first. I try to stay away from medications as long as I can. You can leave your filter media in while you do salt, too.

Check you ammonia and nitrate levels and let us know where they are at.