Ok, so I have two bettas in 1 gallon tanks. One of which has mild fin rot. Both tanks have little diy sponge filters and I do weekly wc's and don't overfeed. Why would only one of my guys be getting fin rot, is he just less hardy. I handle each take exactly the same. Any suggestions, or reasons why this would occur. I put a pinch of salt in each tank as well. I'm just stumped, they're both healthy and active.
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