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Learn how to test your aquarium water. Poor water quality stresses fish, which leaves them susceptible to disease and possibly death.
Updated on October 23rd, 2025
Learn how to safely handle your aquatic life to avoid toxin & bacterial exposure. Find aquatic life care supplies at your neighborhood Petco pet care center.
Updated on October 23rd, 2025
Learn how to care for a Koi, recommended diet and aquarium setup. Find Koi for sale, supplies and equipment at your neighborhood Petco.
Updated on April 9th, 2026
Before establishing an aquarium at home, learn more about the basics of fish care.
Updated on June 19th, 2026

Tanks with live plants can be excellent additions to your home, bringing a touch of nature indoors. Learn how to take care of aquatic plants.
Updated on November 6th, 2025
Yes, in order to have a healthy tank and to give your fish the best environment, it is necessary. Here is a good write-up on the reasons why: https://www.petcoach.co/article/water-chemistry-basics-ph-temperature-water-hardness-waste/
Updated on September 24th, 2025
I would recommend to have the water completely changed. New water should be ideally submitted for quality testing. Most pet stores will do this for free or a nominal fee. High ammonia levels, PH imbalances may be responsible for that as well. Oxygen concentration and quality of the filters should be determined as well. Please do not hesitate to contact us again on the forum or by requesting a consultation if you have any more questions or to discuss it any further.
Updated on September 24th, 2025
Monitor water chemistry using a home test kit or submit a water sample for testing. The local Petco may do this for free or for a small fee. Aim for an absence (0 ppm) of ammonia and nitrites with nitrates at 20ppm or less. Perform partial water changes to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Pristine water quality is the foundation for healing and recovery from infection or injury in fish. You can use plain aquarium salt (NOT table or Epsom salt) as a general tonic to reduce stress, improve gill function and aid in recovery. Dissolve 1 teaspoon of salt per gallon of water in a cup or two of water and gently pour it into the tank. Treat for 14 days then reassess the condition. An "all in one" product, such as Lifeguard (by Tetra), can be used concurrently to treat infection or parasites. Find one in the aquarium section of the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
Updated on September 24th, 2025
Before you buy any fish, you will need to set up the tank. A basic set up includes: a tank, filter, hood/light, heater, gravel and some decor. The tank should run without fish for at least 4 to 6 weeks. This gives it time to cycle. The Nitrogen Cycle is critical to the health of the tank and any fish you will be keeping. During this time, beneficial bacterial will populate the filter and substrate (gravel). These bacteria will be responsible for breaking down fish wastes and other wastes (uneaten food, dead plants, etc.). You will need a home test kit to monitor water chemistry (ammonia, nitrites, nitrates, pH) or you will have to submit water samples for testing. Most pet stores will do this for free or for a small fee. At first, you will see high levels of ammonia and nitrites. Over time, as bacteria grow, these levels will drop. When ammonia and nitrites are at 0 ppm and nitrates are below 20 ppm, you can consider adding fish. Regular (every 1 or 2 weeks) partial water changes as well as filter changes will be needed to maintain stable water chemistry and adequate water quality. The size of your tank will determine what fish and how many you will be able to keep. Most Tetras do best in groups, so a 12 inch tank may not be large enough. There are several article in the Petco Pet Education Center, formerly Petcoach Library that will provide more detailed information. Click on "Educational Center" at the top of the page, then scroll down to "Articles" and click. Use the Search Bar to find articles regarding aquarium set up and fish keeping.
Updated on September 24th, 2025
It is possible the tank has not cycled properly which results in high ammonia and nitrite levels which can kill fish. Allow the tank to run, without fish, for at least 4-6 weeks. During this time, use a home test kit or submit a water sample for testing every few days. The local Petco may do this for free or for a small fee. What you are looking for is to have ammonia and nitrites at 0 ppm and nitrates at 20ppm or less. pH can hover around 7 for most community fish. Avoid large, rapid swings in pH though. What is happening in the tank during this time is that beneficial bacteria are populating the gravel/substrate and the filter. These bacterial populations are responsible for the Nitrogen Cycle. This cycle breaks down wastes from fish, uneaten food and plant matter into by-products that are filtered out or dissipate. You can "cycle" a tank with fish, however this increases the risk of loss. Once your tank has cycled, you can add fish. You will still need to monitor water chemistry and perform partial water changes regularly. Use only conditioned water that is temperature matched to prevent stress or shock. You will also need to vacuum the gravel regularly and rinse the filter media. Never use tap water to rinse. Use a bit of tank water to protect bacterial populations in the sponge.
Updated on September 24th, 2025