To clean a freshwater fish tank, when we say cleaning, we probably mean maintaining. You want to clean your tank once a week, every two weeks, once a month, depending on how dirty it is, how many fish, and how much you feed. Every tank is going to be a little bit different, but the cleaning methods are pretty much the same. The goal of cleaning an aquarium is to get a lot of the waste out of the water with minimal shock to the environment. Remember, there is bacteria that's growing in the filter, on the sand bed, and even on the glass and decorations in the aquarium. You want to minimize the shock to this bacteria because this bacteria is what's responsible for keeping your water safe for your fish. It's constantly growing and breaking down waste. It's breaking down ammonia and nitrite and keeping that water really, really clean and safe for the fish.
When we go in there, we clean it and we change half the water and our filter, we're shocking the system. We could almost do more harm than good by cleaning our fish tanks. The key is really to do regular maintenance, not to wait until the tank gets really, really dirty, the filtration stops working, and the water is really cloudy. That's when you're going to be setting yourself up for a disaster after you clean the tank. I've seen many people when they clean their aquarium, the water is cloudy for a week or two after that because the bacteria is so shocked.
To clean your aquarium, you want to do regular water changes. I recommend 15 to 20 percent every two to four weeks, again, depending on the stocking density of your aquarium. You want to invest in a good gravel cleaner, a siphon, a bucket, a good algae pad, and some test kits and dechlorinators. You want to change the water. As you're taking 15 to 20% of the water out, you want to go through the sand bed or the gravel bed very, very slowly and remove a lot of the waste that has been settled in that gravel. You'd be amazed at what gets trapped in the gravel. It's really, in my opinion, your best filter, your gravel bed.
You want to free that up, get a lot of the waste out. Flush it down the toilet. Make sure you don't dump any gravel down the toilet or you're going to have to call a plumber. When you put new water back in the aquarium, you want to make sure the pH and the temperature is stable. It's good to let water sit overnight so it has a change to degas. A pH test kit and some pH up, pH down, whether in liquid or in dry powder form will be beneficial to help getting the pH back to where it is. You want to match the pH to what it was in the aquarium. The main thing is to not shock your aquarium.
If you haven't done a water change in a while, make sure your pH of the new water matches your existing water. What that means is your pH could be as low as 6.5 even though it's supposed to be at 7.0. The new water is probably going to be 7.4 to 7.6. You'll shock the aquarium by putting high pH water, so you want to bring the pH down in the new water before adding it.
As far as your filtration, you want to clean the filtration in a manner that's not going to shock the bacteria, cleaning the filters in water from the aquarium in a bucket. Even in the dirty water, you can squeeze out your filtration and then put it back in. Replace the carbon, that's going to keep the water free from getting a lot of organics and yellow. Again, don't shock it and do it regularly. Those are the best practices.