Who Gives A Fish Forums

I'd double-check the heater too. Sometimes they malfunction and the temp swings without you noticing. A digital thermometer's a cheap way to rule that out.

If all else fails, consider a salt bath. Just 1 tsp per gallon of aquarium salt in a quarantine tank for 10 minutes can help with general sluggishness. But don't overdo it—bettas are freshwater fish after all.

Honestly, sometimes they just have off days. Mine will lounge around like a couch potato for a day or two, then bounce back like nothing happened. Keep an eye on him but don't stress too much yet.