Water parameters in a betta's tank are critical for their wellbeing. If he lives in water that is too warm, acidic or alkaline for his body to properly absorb essential vitamins and minerals; or contains too much ammonia or nitrates he could become unhealthy and eventually sick; when conditions meet ideal water parameters he'll become active and eager to feed!
For optimal aquarium water conditions, tap or spring water that has been treated is ideal. Tap water should be treated with a fish-safe chemical that neutralizes chlorine and chloramine levels that could harm tropical fish species. In addition, having a test kit available to you for measuring pH, hardness and ammonia/nitrite levels in your tank is crucial.
Ideal aquarium water should have a GH range between 3-4dGH. The dGH measures how much magnesium and calcium have dissolved into your aquarium water. Utilizing a water conditioner, adding Indian almond leaves or driftwood pieces or even boiling RO/distilled water can all help naturally lower its GH value.
Water changes should be completed on an aquarium's size and filtration system to maintain optimal conditions and prevent build-up of organic material in your tank. Doing this also keeps its pH balance balanced to avoid acidification, alkalization or becoming dirty; additionally, regular water changes help ensure your betta avoids eating any harmful bacteria or parasites found in its soil or substrate.