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Learn how to care for semi-aggressive fish, recommended diet & aquarium setup. Find the right food, supplies & equipment at your neighborhood Petco.
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Wondering why you may need CO2 in your fish aquarium? Learn the basics from a Petco aquatics specialist.
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Search Petco to learn about blackwater fish aquariums. We want to help you decide what lifestyle is best for your unique fish.
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Learn how to care for your Cichlid, recommended diet and tank setup. Find the right food, supplies and equipment at your neighborhood Petco.
Updated on April 9th, 2026
Thanks for reaching out about you fish. It is believed to be a Comet goldfish. Water quality and nutrition is the key to success. Testing water parameter for pH, ammonia, nitrite and nitrate will give you guidance for a healthy environment. Purchased food should be rotated out every 3 months as vitamin C and other nutrients degrade over time. Trying to maintain water temperature can be challenging with out a heater, but most fresh water fish tolerate some changes. Good luck.
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
There are several causes that can provoke these signs fro water imbalances to specific diseases like swim bladder ones. This problem requires a quite radical but logic approach. Begin by submitting a water sample 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. Oxygen concentration and quality of the filters should be determined as well. If water quality is good and there are no major imbalances, your fish should get examined to look for any sign of bacterial/fungal infection and eventually water should be treated. 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
Check water chemistry first. Use 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 20 ppm or less. Perform partial water changes, no more than 30% at a time, to stabilize chemistry and/or to improve water quality. Use only conditioned water that is temperature matched to prevent stress or shock. Check water temp as well. Any of these can drive a fish to the surface. The "flashing" (darting about) can be due to infection (bacterial, fungal or parasites). Consider a broad spectrum antibiotic or an "all in one" product to treat multiple infections. Look in the Aquarium section of the local Petco for options. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
Updated on September 24th, 2025
Gold fish can make great fish but they can live up to 25 years and require a large tank that may need to be upgraded if they grow too large. Do get at least 2 fish. Here are some links which may help: https://www.petcoach.co/article/chewing-in-puppies-how-to-control-it/ https://www.aqueon.com/information/care-sheets/goldfish https://www.hartz.com/how-to-introduce-new-fish-into-your-aquarium-tank/ I hope this helps and congrats on your new pets!
Updated on September 24th, 2025