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Buying new fish is exciting, but sometimes things do not go as planned. A fish might arrive stressed, sick, or even dead, or the species you receive may not be what you expected. If you are facing an issue with fish you purchased, you are not alone. These situations are common for both beginners and experienced aquarists, and there are clear steps you can take to protect your animals, your tank, and your wallet. In this guide, you will learn how to handle problems right away, what most stores and online sellers usually offer, and how to prevent issues next time. The goal is to help you act quickly and calmly, so your fish and your aquarium have the best chance to thrive.
Understanding Common Fish Purchase Issues
Dead on Arrival (DOA)
Dead on arrival is when a fish arrives lifeless in the bag or dies within hours of unboxing. This can happen even when shipping is done correctly. Causes include temperature swings, oxygen depletion, long transit times, or pre-existing health issues. Most reputable sellers have a DOA policy, but it usually requires that you provide proof within a short window, often within 1 to 4 hours of delivery.
If you experience a DOA, do not throw the fish away immediately. Instead, take clear photos and short videos of the fish in the unopened bag, the shipping label, and the entire shipment. This documentation is often required for a refund or replacement.
Lethargy, Gasping, or Collapse After Acclimation
Sometimes a fish is alive on arrival but seems weak, tilted, or gasping at the surface after you introduce it to your tank or quarantine. The main cause is stress and water chemistry shock. During shipping, ammonia can build up in the bag. When you open the bag, pH often rises, turning non-toxic ammonium back into toxic ammonia. This is why very long acclimation can be harmful for shipped fish.
If the fish is struggling, increase aeration, stabilize temperature, dim the lights, and keep the fish in quarantine. A water conditioner that detoxifies ammonia can help. Avoid chasing or netting repeatedly, as this adds more stress.
Visible Disease Signs
Common signs include white spots like grains of salt (ich), frayed or fuzzy fins (fin rot or fungus), a dusty gold sheen (velvet), ulcers on the body, heavy breathing, or clamped fins. These can be introduced to your aquarium if you do not quarantine. Even healthy-looking fish can carry parasites.
If you see disease symptoms, keep the fish in quarantine and begin appropriate treatment. Do not add bag water to your tank. If you bought the fish locally, you can often return to the store for advice or medicine recommendations. If you purchased online, take photos or video of symptoms and contact the seller promptly.
Wrong Species, Size, or Sex
Misidentification happens, especially with juveniles that look similar or with species that change color as they grow. You might receive a fish that gets much larger than you can house or a male instead of a female. Many sellers will address these mistakes if you reach out quickly with clear photos.
Decide if you can ethically keep the fish based on its adult size and care needs. If not, talk to the seller about return options or store credit. Never release fish into local waterways, as this is harmful and often illegal.
Unexpected Aggression or Compatibility Problems
A fish that seems peaceful in the store can become aggressive in your tank. Territory, tank size, hiding spots, and the order you add fish all matter. Some species simply do not mix well, even if care sheets suggest they might.
If aggression appears, rearrange decor to reset territories, add more hiding places, or use a separator to protect weaker fish. Contact the seller if you were advised the species would be compatible and it clearly is not, especially if the seller recommended the pairing.
Hidden Injuries or Shipping Damage
Split fins, missing scales, or scraped mouths can occur during netting or shipping. Mild damage often heals in clean, well-oxygenated water with a calm environment. Serious injuries can lead to infections and may require medication.
Document injuries right away and keep the fish isolated so you can monitor progress and prevent spread of disease to your display tank.
What Usually Happens with Guarantees and Store Policies
Live Arrival Guarantees
Many online sellers offer a live arrival guarantee. This often covers fish that arrive dead or die within a few hours after delivery. Some sellers extend the guarantee to 24 to 72 hours if the fish was acclimated and quarantined. Read the policy before purchasing so you know what is covered and how to file a claim.
Local fish stores may not offer written guarantees, but many will work with you if you report problems quickly and bring water test results. It helps to establish a relationship with your local store and ask about their policy before you buy.
Refunds, Replacements, or Store Credit
Resolutions usually include store credit, a replacement fish in a future shipment, or a refund. Some sellers prefer credit or replacement rather than refunds. If you do not want a replacement, say so clearly and politely in your message. Most sellers want to make you happy and keep you as a customer.
Make sure you understand how credits work, including expiration dates and whether they apply to shipping costs. Keep your order number and photos in one place so the process goes smoothly.
Who Pays Shipping and Packaging
Even when the fish is covered, shipping costs are sometimes not refunded. Replacements may be combined with future orders to help reduce costs. Cold packs or heat packs may be added depending on weather. Ask for the seller’s best practices for your region and season.
If the issue was clearly due to poor packaging, many sellers will cover shipping on a replacement. This varies by company and by the evidence you provide.
Local Fish Store Considerations
Local stores often allow returns for store credit if you bring the fish back within a set period and show that your water parameters are safe. They may test your water on-site. If your tank is cycling or shows high ammonia, they are less likely to offer a refund because poor water quality is a common cause of fish loss.
Always keep your receipt and ask for a copy of the policy. Polite, honest communication goes a long way.
Exclusions and Fine Print
Some fish are not covered under guarantees, such as wild-caught species, very delicate species, or fish shipped during extreme weather. Guarantees also may be void if you miss the delivery, leave the package outside, or fail to follow the seller’s acclimation and quarantine instructions.
Read the details before ordering. If you are unsure, message the seller and ask specific questions about coverage for the species you want.
Your First Hour Action Plan
Unboxing Checklist
Open the box carefully and check each bag. Count the fish, look for signs of life, and note the temperature of the bag water with your fingers. Take photos and video before opening any bag. Photograph the shipping label and the interior packaging. If anything looks off, you will already have proof.
If the fish arrived during very hot or very cold weather, do not rush. Stabilize temperature gradually and keep the fish in a dim area to reduce stress.
Temperature Management
Float the sealed bag in your quarantine tank for about 15 to 20 minutes to match temperature. If the water in the bag is very cold or very hot, extend the float to 30 minutes, but avoid leaving fish in sealed bags for too long. The goal is to avoid sudden temperature swings that can shock the fish.
Check for breather bags. Breather bags allow oxygen exchange through the bag walls and should not be floated with the fish still inside. If you have breather bags, do not float them. Instead, open the bag, gently pour the fish into a specimen container, and proceed quickly with acclimation.
Acclimation Best Practices
For fish shipped overnight, limit exposure to bag water. After temperature matching, open the bag and add small amounts of your quarantine tank water every few minutes for about 10 to 20 minutes. Add a conditioner that detoxifies ammonia if needed. Then net the fish and transfer it to the quarantine tank. Do not pour bag water into your tank.
For fish bought locally with short travel time, you can do a slower acclimation if the store’s water is similar to yours. If you know the store runs very different pH or hardness, keep it brief and gentle like with shipped fish to avoid ammonia spikes from pH changes.
Quarantine Is Your Safety Net
Always quarantine new fish in a separate, cycled tank for at least 2 to 4 weeks. Quarantine prevents disease from reaching your display tank and gives you time to observe behavior, feeding, and breathing. A simple quarantine setup includes a sponge filter, heater, hiding places, and a tight lid.
Quarantine is also the best way to show a seller you followed proper care if you need to make a claim.
Your First 24 Hours Action Plan
Monitoring Behavior and Breathing
For the first day, keep lights dim and avoid tapping glass or chasing the fish. Look for steady breathing, smooth swimming, and interest in the environment. Gasping at the surface, lying on the bottom, flashing against objects, or clamped fins suggest stress or illness.
Increase aeration with an air stone or slightly higher filter output if breathing is heavy. Good oxygen levels help fish recover from shipping stress.
Testing Water Parameters
Test ammonia, nitrite, nitrate, pH, and temperature. In a healthy, cycled quarantine tank, ammonia and nitrite should be zero. Nitrate should be under about 20 to 40 ppm. Keep the temperature steady at a level appropriate for the species. Sudden changes are more harmful than slightly imperfect values.
If ammonia or nitrite is present, do a partial water change and add a conditioner that detoxifies ammonia and nitrite. Re-test a few hours later to confirm improvement.
Feeding or Not Feeding New Fish
Many new fish will not eat on day one, and that is normal. Offer a very small amount of high-quality food after the fish has settled, and remove uneaten food to keep water clean. For picky species, try live or frozen foods to encourage appetite. Do not overfeed while the fish is stressed.
The First 7 Days: Stabilize and Observe
Should You Treat Proactively
Some aquarists use a preventive course of salt or mild antiparasitic treatment. If you are new to medications, start with observation and only treat when you see clear symptoms. Over-medicating can harm fish and your biofilter. Use salt for livebearers and many freshwater fish to support gill function, but avoid salt with sensitive species and plants if they share the tank.
For marine fish, quarantine protocols often include copper or other medications, but copper must be measured precisely. If you are unsure, consult your local store or a trusted reference before dosing.
Light, Stress, and Hiding
Keep lights low for the first few days. Provide caves, plants, or PVC pieces for hiding. A calm environment speeds recovery and reduces aggression. Cover three sides of the quarantine tank if the fish appears skittish.
Reduce sudden movements near the tank and keep noise low. Consistency is more important than perfection during this period.
When to Move into the Display Tank
After two to four weeks without symptoms, consistent eating, and stable water, you can move the fish to the display tank. Make sure the display tank is appropriate for the species and that you have a plan for introducing the new fish to tankmates, such as rearranging decor to reduce territorial claims.
If you spot any illness during quarantine, restart the observation timer after treatment is complete and the fish looks fully recovered.
If a Fish Arrives Dead or Dies Shortly After
Documentation That Sellers Require
Take clear photos and short videos of the fish in the unopened bag if DOA. If the fish dies after opening, take images with a time stamp, the tank setup, and any water test results. Keep the shipping label and packaging. Save emails or texts related to the order. Most sellers need this evidence to issue credit or a replacement.
Send your documentation within the time window listed in the guarantee. Waiting too long often voids coverage.
How to Communicate with the Seller
When you write, be direct and polite. Share your order number, the species, what happened, and the steps you took. Include photos, short video links, and your water test results. Ask for the type of resolution you prefer, whether that is a refund, store credit, or a replacement on your next order.
A helpful message might say that the fish arrived at a certain time, you floated the bag for a set number of minutes, you acclimated for a set time, you did not mix bag water into your tank, and you quarantined. Clear details build trust.
Safe Handling and Disposal
If the fish has died, do not flush it. Place the fish in a sealed bag and dispose of it in household trash, or bury it in the yard if allowed. Wash your hands, and disinfect any buckets or nets used. If disease is suspected, use a safe aquarium disinfectant on equipment.
Handle all fish respectfully. Avoid leaving deceased fish where other animals can access it.
What to Do with Tankmates and Equipment
If the fish died in quarantine, continue to observe the quarantine tank for signs of illness. Consider partial water changes and enhanced aeration. If the fish died in your display tank, watch tankmates closely for two weeks. Early signs of disease might include scratching, spots, frayed fins, or rapid breathing.
Do not rush to medicate the entire tank unless you see clear symptoms. Stable, clean water and patience are your best tools.
When the Fish Is Sick but Alive
Triage Steps You Can Do Right Now
Increase aeration with an air stone to improve oxygen levels. Check temperature and adjust slowly toward the ideal range for the species. Add a water conditioner that detoxifies ammonia and nitrite if tests show any level above zero. Dim the lights and reduce stress.
For many freshwater fish, a small amount of aquarium salt can help with gill function and reduce osmotic stress. Research your species first, because some fish and plants are salt-sensitive.
Common Illnesses and First Responses
White spot disease, or ich, shows as tiny white grains on fins and body. Raising temperature gradually, when safe for the species, and using a proven ich treatment can help. Velvet looks like a gold dusting and needs prompt treatment with the correct medication and darkness for part of the cycle. Bacterial fin rot appears as ragged fins and can improve with clean water and, if needed, a targeted antibiotic in quarantine.
When in doubt, gather clear photos and ask for help from your local store or a trusted aquarium forum. Always dose medications according to directions and avoid mixing multiple drugs unless recommended by an expert.
When to Request Partial Refunds or Support
If the fish arrived with visible illness or failed to thrive despite proper acclimation and quarantine, contact the seller. Share your photos and water tests. Some sellers will offer store credit or send medication advice. Others may offer a replacement in a later shipment.
Be honest about your setup and steps taken. Sellers are more likely to help when they see that you cared for the fish correctly.
Avoiding Common Mistakes
Do not pour bag water into your tank. Do not extend acclimation for hours with shipped fish, because rising pH can increase ammonia toxicity. Do not skip quarantine. Do not overfeed a stressed fish. Do not tear down your entire display tank at the first sign of trouble. Think calmly and act methodically.
Misidentification, Wrong Size, or Sex
Gathering Evidence and Reaching a Resolution
Take clear photos of the fish in good light, and include a ruler or familiar object for size comparison. If the sex is wrong, try to capture the distinguishing features, such as fin shape or color differences. Send these to the seller with your order number and a brief, polite explanation.
Many sellers will offer credit or replacement when a mistake is clear. Keep communications professional and solution-focused.
Deciding to Keep or Return
Ask yourself whether you can meet the fish’s adult size, behavior, and water needs long-term. If the fish will outgrow your tank or harm current tankmates, returning or rehoming is the ethical choice. Work with the seller or your local store to find a good solution.
If you keep the fish, adjust your aquascape, filtration, and feeding plans to match its needs. Research the species thoroughly so you can provide a happy, healthy home.
Long-Term Care If You Keep the Fish
Provide the correct diet, more hiding places, and appropriate tank size. Monitor interactions with tankmates and be ready to separate fish if aggression appears. Keep notes on growth and behavior so you can make changes early.
Remember that a misidentified fish is not the fish’s fault. Proper care makes the best of an imperfect situation.
Aggression and Compatibility Problems
Rescaping to Reset Territories
Many aggression problems improve when you rearrange decor to break line-of-sight and create new territories. Add more caves, plants, or rockwork to spread out hiding spots. Introduce the new fish after the changes so no one has a home-field advantage.
Feeding a small meal before introductions can also reduce tension. Keep lights dim during the first day together.
Timeouts, Breeder Boxes, and Dividers
If a fish is bullying others, use a tank divider or breeder box to give both fish a break. Timeouts can last a few days to a week. This lets injured fish heal and helps reset social order. Make sure the separated fish has clean water and steady oxygen.
Remove the divider when the aggressor loses interest and both fish are eating well. Be ready to re-separate if aggression returns.
Rehoming Options
If aggression does not improve, consider rehoming the fish. Your local store may accept returns, or you can find a hobbyist group or club to take the fish. It is better to rehome than to let a fish live in constant stress or injury.
Ask the seller for help if their recommendation contributed to the mismatch. Many will assist in finding a solution.
Consumer Rights and Ethical Considerations
Know Your Local Laws and Policies
Consumer protection laws vary. Some regions give you clear rights for returns on defective or mis-sold goods. Live animals are often handled differently, but stores still must follow stated policies. Keep receipts and email records.
If you paid with a card or online platform, there may be dispute processes for unresolved issues. Always try to resolve directly with the seller first.
Be Fair to Small Businesses
Most fish sellers are passionate people who care about animals. They face risks with every shipment. When you report a problem kindly and with proof, you make it easier for them to help you. Avoid public complaints until you have tried private resolution.
Honest, respectful communication results in better outcomes for everyone, including the fish.
Avoiding Impulse Buys
Many fish problems start at the point of purchase. If you buy a fish without researching, you may face size, diet, or aggression issues later. Take time to read care guides, check adult size, and confirm tank compatibility before you buy.
Patience is a key skill in fishkeeping. The right fish at the right time will save you stress and money.
Preventing Issues Before You Buy
Research the Species and the Source
Learn the fish’s adult size, temperament, water parameters, and special needs. Read multiple sources so you get a balanced view. Look for reviews of the seller or store. Consistent positive feedback is a good sign.
Avoid buying during extreme heat or cold if shipping is involved. Good timing reduces stress for your fish.
Ask the Right Questions
Ask the seller what the fish has been eating, how long they have held it, and what parameters it is kept in. For online orders, ask about packaging, heat or cold packs, and guarantees. For local stores, ask if they will test your water and what their return policy is.
Clear answers build confidence and help you prepare your tank properly.
Choose Healthy Specimens
Look for fish with clear eyes, smooth swimming, full bellies, and no visible sores or frayed fins. Watch the fish for a few minutes. A healthy fish should show interest in its surroundings and respond to movement. Avoid fish that breathe heavily, hide constantly, or float oddly.
If you see illness in the store tank, do not buy from that tank. Pathogens can spread between fish quickly.
Prepare the Quarantine Tank
Have your quarantine tank cycled and ready before you order or bring fish home. Include a sponge filter, heater, and hiding places. Keep water test kits on hand and make sure you can perform small, frequent water changes.
Preparation is the easiest way to turn potential problems into minor bumps instead of big setbacks.
Quick Answers to Common Questions
What if my fish arrived cold or hot but alive
Stabilize temperature slowly. Float sealed bags to match temperature, then acclimate briefly and transfer fish to quarantine. Increase aeration and keep lights low. Avoid long acclimations for shipped fish to prevent ammonia toxicity.
Monitor for stress signs. If the fish was clearly mishandled during shipping, document and contact the seller.
How fast should I contact the seller about a problem
Right away. Many guarantees have short windows. Send photos and details within hours if possible. Waiting may void coverage, even if the issue was not your fault.
Keep your tone calm and factual. Sellers are more willing to help when communications are clear and prompt.
Can I get a refund if my tank parameters were bad
Usually not. If ammonia or nitrite is present, most sellers will not cover losses because water quality is a leading cause of death. This is another reason to quarantine and maintain a fully cycled tank before buying fish.
Share your test results honestly. Good stores may still offer advice or partial credit, but it is not guaranteed.
Conclusion
Having an issue with a fish you purchased is frustrating, but it is also part of the learning curve in fishkeeping. The most important steps are to act quickly, document everything, and quarantine new arrivals. Understand your seller’s policy, communicate politely with clear evidence, and follow safe acclimation practices. Most problems can be managed with calm, steady care, and many sellers will work with you to make things right.
Over time, you will prevent many issues before they start by researching species, choosing healthy fish, preparing a proper quarantine setup, and maintaining stable water. When trouble happens, do not panic. Give your fish clean water, oxygen, gentle handling, and time to settle. With a good plan and a bit of patience, you can turn a disappointing situation into a successful recovery and enjoy a thriving, peaceful aquarium.