Fish In need

I have another betta, had him for a while now because he was so pretty I couldn’t leave him at Walmart but he’s doing perfectly on the same diet however to be safe I am swapping him to the omega 1 pellets and frozen food. His name is opal. He’s not in as large a tank as garnet Was. However I’m going to try and learn more about taking care of a larger tank (and deep clean it) before I swap him into it. I had a betta a long time ago who was extremely lonely and got sick until I bought another betta to keep in a nearby tank, I’ve been buying two bettas at a time since.