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Why Should You Wait 24 Hours to Add Fish to a Tank?

Why Wait 24 Hours to Put Fish in Your Tank San Diego, CA

There are various opinions among aquarists and those who sell fish tank supplies about how long they should wait to add species to new tanks. Some purists who wrongly wish to go step by step and follow the “more natural” process of building and establishing an ecosystem say you should wait as long as three weeks, but that has proven to be a silly waste of three weeks without fish. Others prefer a more expedited process that includes the introduction of bottled bacteria and a small amount of fish, which can cut down the process to 24 hours before species can be introduced and is very simple.

Understanding Established Tanks

An established aquarium is one that has been through at least one nitrogen cycle with a small amount of healthy fish and a small amount of fish food to grow the bacteria. For instance, the tanks you see at an aquarium shop are healthy and established. In this case, the aquatic ecosystem has been transplanted to a new container, one filled with water that has the proper pH, nitrogen, chlorine, and bacteria levels that can sustain fish.

Preparing a New Tank

Everything starts with the location of the tank. You’ll need external factors to support the aquarium, including a solid and stable surface, natural light, and nearby electricity outlets where you can connect aerator pumps, thermostats, and lamps. The next step is to determine the size of the tank, the gravel, decorations, and plants. The tank, gravel, and all objects that will go inside the tank need to be washed with warm water only. The plants can be washed with water right out of the tap. The gravel is placed first before filling one third of the tank with water.

Treating the Water

Follow the instructions to pour additives and conditioners. Pay attention to the recommended waiting times. Wash and dry your hands before introducing plants and connecting the filters. Once the pump begins to circulate the water, the bacterial bloom process will begin, and you’ll get to see it after you introduce fish. The various establishment methods start to vary at this point. If you introduce bottled bacteria and water from an established tank at the shop, the nitrogen cycle can be completed after 24 hours.

Testing the Water and Adding Fish

It will take about a day for the chemicals to eliminate chlorine and bacteria to bring ammonia and nitrates to healthy levels for fish to live in. Test the water once before setting a 24-hour timer and test it again before adding fish. It’s strongly recommended to start with just a couple of resilient species and let them enjoy the aquarium for two to three weeks before introducing more species. You’ll get to see the bacterial bloom when the water turns cloudy before clearing up to let you know the tank has been established.

There are several supplies you’ll need to maintain your tank and ensure its inhabitants can remain healthy and happy. Whether you need an aquarium dosing pump, beneficial bacteria, a heater or cooler, or any other aquarium supply, you can find what you’re looking for at Aquatic Warehouse. Call one of our aquarium experts today at 858-467-9297 if you have any questions.


Contact Information

  • Address: 5466 Complex Street Suite 204
    San Diego, CA 92123
  • Phone: (858) 467-9297
  • Email: sales@aquaticwarehouse.com
  • Working Days/Hours: Mon - Fri / 10:00 AM - 7:00 PM
    Saturday / 10:00 AM - 6:00 PM
    Sunday / 11:00 AM - 6:00 PM


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