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Related Articles & Questions
- Care Sheets
Freshwater Shark Care: Ultimate Guide to Tank, Feeding & Compatibility
Freshwater Sharks are not true sharks, but are typically catfish or relatives of carp. Learn how to take care of freshwater aquarium sharks, food, tank size.
Updated on April 9th, 2026
- Care Sheets
Barbs Fish Care Guide for Beginners: Tank, Food & Compatibility
Learn how to care for Barbs fish, recommended diet and aquarium setup. Find Barbs for sale, supplies and equipment at your neighborhood Petco.
Updated on April 9th, 2026
- Care Sheets
Brackish Water Fish Care: Your Complete Guide to Tank, Food & Species
Learn how to care for brackish water fish, recommended diet & aquarium setup. Find the right food, supplies & equipment at your neighborhood Petco.
Updated on April 9th, 2026
- Care Sheets
Build Your Thriving Saltwater Tank: Easy Setup for Marine Life
Learn how to set up a saltwater fish tank and key considerations regarding placement, supplies needed, and the overall set up process.
Updated on October 23rd, 2025
- Care Sheets
Ultimate Large Marine Angelfish Care Guide: Setup, Diet, Companions
Learn how to take care of Large Marine Angelfish, recommended diet and tank setup. Find the right food, supplies and equipment at your neighborhood Petco.
Updated on April 9th, 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
- Training & Behavior
Moving fish long distance: How to transport and feed them safely?
Thanks for reaching out. If is a good idea to fast for 1-2 days prior to shipment, this decreased feces and will help to keep the ammonia down. Typically clear bags are utilized with about 50% water, and 50% air/oxygen used. A local pet store might be able to assist, as they get shipment in (so have older bags and boxes, which need to be disinfected) and hopefully the skills to ship. Check with the airline also, box needs to be well labelled "LIE ANIMALS" and "THIS END UP". Sometimes a health certificate for interstate travel is needed, so contact airline and State of Utah, veterinarian. Good luck.
Updated on September 24th, 2025
- Health & Wellness
Glofish shark has long, stringy white poop. What should I do?
He may have internal parasites. maintain pristine water quality and confirm stable water chemistry. This can be done by using a home test kit or by submitting a water sample for testing. The local Petco may do this for free or for a small fee. Perform a partial water change, no more than 30% total volume at a time, if indicated. use only conditioned water that is temperature matched to prevent further stress or shock. Check the water temperature as well, since low temps can affect activity, appetite and digestion in fish. Anywhere between 72 F and 80 F is acceptable. Keeping it at the higher end may aid in digestion and defecation. Consider a broad spectrum parasite medication. You can find one in the Aquarium section at the local Petco. Follow label directions carefully and remove the carbon filter insert during treatment if indicated.
Updated on September 24th, 2025
- Health & Wellness
Just got a small fish. What breed is it and how do I care for it?
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
- Training & Behavior
Will rainbow sharks, guppies, and neon tetras get along in a tank?
Rainbow sharks are generally aggressive with other fish and are not a good match with peaceful fish. Tetras and guppies are generally fine to live together. When picking out fish, you want to keep a community that all have the same aggression levels. The store clerk will be able to help you with that information. I hope this is helpful and please feel free to post any additional questions.
Updated on September 24th, 2025
