Two Easy Ways to Start Earning Rewards!
Become a member today!
Members-only pricing and offers, personalized care notifications, Vital Care points back on every purchase and more!
Become a credit card member today!Earn 2X Pals Rewards points at Petco
when you use Petco Pay!APPLY NOWLearn More About Petco Pay Benefits
AA Aquarium Aquarium Equipment
Get It Today
Related Articles & Questions
- Home & Habitat
Freshwater Aquarium Plant Maintenance Guide
Learn how to pick the right aquarium plants, substrate, lighting, and fertilizers to ensure that your aquarium plants thrive and stay healthy.
Updated on July 17th, 2026
- Home & Habitat
How to Set Up a Fish Tank: Complete Setup Guide
Everything you need to know about how to start a fish tank. Learn about setting up an aquarium, choosing the right type, and acclimating new fish to your tank.
Updated on June 19th, 2026
- Home & Habitat
CO2 for Fish Aquariums: What Every Pet Parent Should Know
Wondering why you may need CO2 in your fish aquarium? Learn the basics from a Petco aquatics specialist.
Updated on July 17th, 2026
- Care Sheets
Essential Large Marine Fish Care Guide: Tank Setup, Diet, & Tank Mates
Learn how to care for large marine fish, recommended diet and habitat setup. Find the right food, supplies and equipment at your neighborhood Petco.
Updated on April 9th, 2026
- Home & Habitat
Marine Aquarium Clean Up Crew: Complete Guide
Visit Petco to learn about cleanup crews and how they can help your aquarium health.
Updated on June 19th, 2026
- Vet Q & A
Why are my fish dying with bleeding, white spots, and polluted water?
I'm sorry you are having difficulties with your aquarium. There are several issues that should be dealt with right now. They are water chemistry, aquarium size and choice/number of fish. Any new aquarium should be set up and, ideally, run empty for several weeks (usually 4-6 weeks). This is so beneficial bacteria have an opportunity to populate the substrate and filter. These bacteria are necessary to break down wastes that fish will produce. The technical phrase for this is "establishing the Nitrogen cycle". These bacteria will break down wastes into ammonia then nitrites then nitrates. Nitrates can then dissipate or be absorbed/used by live plants. In high enough concentrations, ammonia and nitrites are toxic and can kill fish. Cycling a tank with fish is possible but it increases the risk of loss. Water chemistry should be checked every few days using a liquid home test kit. A water sample can be submitted for testing , but is not as convenient as testing yourself. Most pet stores or fish stores will do this for free or for a small fee. Partial water changes, no more than 30%, can be done as needed to stabilize chemistry and maintain water quality. Choices for water conditioners include NovAqua, AmQuel Plus, Prime, StressZyme or StressCoat. Tank size is another concern. With most fish, the widely accepted "one inch of fish per gallon" will be sufficient. For koi and other carp species, including goldfish, the rule is not sufficient. At full size, goldfish need 20 gallons per fish with an additional 10 gallons for each additional fish. Koi do best in larger tanks, much larger...we're talking in the hundreds of gallons or small ponds. These species produce a larger than average bio-load (wastes) that can quickly affect water quality in a tank. To combat this, large water volumes and powerful filtration are required. Any filter should be rated for at least twice the tank volume. I'm not sure what size tank you have now, it may be fine if the fish are young and small, but they will quickly outgrow it. The last issue is choice of fish. Koi and goldfish are cold water fish. They do best in water between 65F and 72F. Most species of sharks do best in the high 70sF to low 80sF. Keeping fish in incorrect water temperatures will lead to stress and illness. This could be compounded by the water quality/chemistry issues you are having currently. Until the chemistry is stable and water quality is maintained, your fish will continue to become ill and possibly die. Any treatment will not be successful in this situation. Do not purchase or add any more fish until the tank has cycled. If you have additional questions, you can post them in the forum or request a consultation to discuss the case in greater depth.
Updated on September 24th, 2025
- Vet Q & A
How to gradually raise my goldfish tank's low pH to the ideal range?
Here is a helpful link: https://www.aqueon.com/information/care-sheets/goldfish Your local aquarium store will likely carry a powdered product to add to the water to increase the pH. The package will have dosing instructions. I hope this helps and please feel free to post any additional questions.
Updated on September 24th, 2025
- Vet Q & A
My aquarium has high ammonia and nitrates. How can I fix it?
The best and safest method is through daily partial water changes, about 30-40% of total tank volume. Use only aged or conditioned water that is temperature matched to prevent stress or shock. Recommended water conditioners are AmQuel, NovAqua and StressCoat. These can be purchased online or in most pet stores or fish stores. A home test kit should be used to monitor levels. If a tank is properly cycled, beneficial bacteria will break down these toxins. Overfeeding, excessive light or heat and dead plants can cause spikes in ammonia and nitrite levels.
Updated on September 24th, 2025
- Vet Q & A
My fish have red gills after moving tanks. Is it ammonia poisoning?
Hi, You will need to test for ammonia, nitrite and nitrates now that there are fish in the new tank. If the biofilter is not well established in the new tank, then the abrupt presence of fish will cause an ammonia spike. You should do a partial water change, ensure proper aeration of the water. There are products you can get to boost the biofilter if this is in fact the issue. You should also consider the number of fish for the just meet of gallons in the tank as overcrowding may be a contributing factor. If you need further guidance, please don’t hesitate to request a consult. Good luck!
Updated on September 24th, 2025
- Health & Wellness
How to humanely euthanize a sick or suffering aquarium fish?
Thanks for reaching out about your fish. Clove oil (eugenol) is approved in the United States as an anesthetic for fish, no sure about Norway. Overdosing on anesthesia is probably the most humane. Freezing or other methods are not acceptable. Fish veterinarians might have access to tricaine methansulfonate (MS-222) another approved anesthetic for fish. A fish veterinarian might also be able to diagnose and treat a problem. Age is not a disease. Good luck.
Updated on September 24th, 2025
