All tanks need at least weekly-to-twice weekly water changes and water changes based on water prams of-Ammonia, nitrite 0.25ppm or greater and Nitrate of 40ppm or greater-It is best to keep nitrate under 20ppm.
When you have filter you need to rinse the filter media regularly , vacuum the gravel weekly with weekly water changes
5-9gal with a filter you need to do Weekly 50% with vacuum. And since you want a snail in his tank you can do additional 2-25% water changes a week.
Filter and cartridge If it is an "all-in-one" cartridge that is filter floss with carbon inside, just rinse it once a week in tank water or dechlorinated water. Most of the filters use those kind of cartridges. If the cartridge becomes too old or starts to fall apart, put a new cartridge in the filter but keep the old one behind it for a week and monitor for ammonia spikes.
When you vacuum-Unplug both the filter and heater-Then plunge the vacuum deep into the substrate and as the mulm/debris clear in a second or two-move and repeat.
Once you refill with like temp dechlorinated water and turn the filter back on the water should clear within the hour-even without a filter the water should clear. If not, you either missed a water change, over feeding or overstocked.
Remember-to always wash hand well before and after working on your tank/Betta. And to unplug both the heater and filter...Safety for both you and your wet-pet.....
If it too much for you then you don't have to use a filter. Filters are optional for bettas. You can just alternate one week 50% , next week 100% water changes. And you need to acclimate betta when you do 100% water changes to new water temperature.
Flakes cause swim bladder issues more readily than most pellets. Use a high quality protein based pellet with the first two or three ingredients as whole fish not fishmeal or wheat. The flakes will also muck up his water quickly , that means ammonia builds up much more quickly.
If you can find Omega One betta pellets and New Life Spectrum for him. And always remove uneaten food. If you give him freeze dried blood worms , use them for a snack 2-3 time a week, they also can cause bloating.
Temperature: Perfect is 76*. You don't have to make it 80*. I personally think the warmer is the temp - more chance for infections.