While you’re changing the water, vacuum the gravel (substrate) to remove all of the leftover food. If the old food remains in the tank, it’ll decay and cause ammonia and phosphates. When vacuuming, remove each rock and decoration so you’ll be able to vacuum efficiently around the entire tank. Be careful not to suck up your betta fish. If you’ve got a filter system under your gravel, vacuum more frequently to avoid nitrates forming. There may be some excessive algae on the glass and different ornaments; scrape all of that off. You can try this by using a special soap-free, non-abrasive clean sponge or brush that you only use to clean your tank. Depending on what quantity water you plan on changing, measure the correct quantity of water conditioner, and keep it readily available. Remember to unplug all connected fish tank heater, lights and filters. Anything that’s connected electrically must be unplugged. Next, collect the siphoned water in a container or measuring bucket. Once you siphon the correct quantity of water, replace all the decorations and rocks that were removed for cleaning.