Sudden betta death
Came home today to find my betta dead at the bottom of the tank. He was fine yesterday, eating and swimming as usual.
I'm wondering if he could have gotten trapped at the bottom and suffocated? I changed the tank about a week ago and took out the gravel I was using and added large river rocks instead (the gravel kept going down my disposal whenever I cleaned the tank). Is it possible he swam into a crevice between the rocks and couldn't swim out? If he was sick then I'm worried about his tankmate (divided tank) getting sick too. Any advice or opinions would be appreciated.