fresh water aquarium - how often should you change the water

How Often Should Water Changes Be Done?

As a new aquarist, I was always wondering how many times a month I should do a water change. When I bought my first aquarium, it was from a guy on Craigslist and he told me that he used the gravel vacuum every few months. Well, when I got the aquarium home and started cleaning it, it looked as if he had not done a water change in several months. I decided to a bit more research on the subject and depending on the size of your tank, the fish you are keeping, and how well your tank is filtered, water changes need to happen every 1-2 weeks.

What I Do

I currently have a 36 gallon freshwater tank with a tropical community – an angelfish, a rainbow shark, 2 bristlenose plecos, a bumblebee catfish, and a few smaller tetras. I change the water in this tank once a week because I am stocked to the absolute maximum capacity and I like to keep my water crystal clear and free of parasites. When I do a water change, I use my gravel vacuum to clean feces and leftover food out of the gravel. In the process of this deep gravel cleaning, the water is being removed from the tank and thus performing a water change simultaneously. I clean the gravel until about 40% of the water has been drained then I refill with room temperature tap water and treat the whole tank with water conditioner.

In my 10 gallon cherry shrimp tank, I also perform a water change every week, but I do not use the gravel vacuum for fear that I may suck up a shrimp. Cherry shrimp have a very small bioload which means the feces should be okay to naturally degrade in the substrate without having to vacuum it out. However, shrimp being invertebrates, they are very sensitive to things like nitrate poisoning, so a water change is required every week. This goes back to knowing what kinds of animals you have and what their requirements are as far as water quality goes.

Remember These Important Points

  • Always perform a water change on schedule. I do mine every Sunday before I get a shower in the morning. If I stay to this schedule, I can be sure that it gets done every week without question.
  • Even if the water looks clear, still do the water change. Deadly parasites, bacteria, ammonia, and nitrates can build up in the water and injure your fish. Your water can be filled with bad bacteria and still be crystal clear, so never slack off just because the water isn’t dirty.
  • If your fish are sick with ich or a similar disease, perform water changes more frequently.
  • Always use a water conditioner like SeaChem Prime after adding new water to your aquarium.
  • If possible, clean the substrate while you’re doing the water change. This kills two birds with one stone.
  • Change at least 30% of the tank’s water every time you do a water change unless your fish require otherwise.
  • If you have live plants, simply vacuum around them – uprooting the plants every week will stop them from developing deep root systems that they need to grow.
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