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When a fish stops eating, it can be scary. Food is a basic sign of health, so a loss of appetite often means something is off. The good news is that most cases have a clear cause and a fix. In this guide, you will learn the most common reasons fish won’t eat, how to quickly triage the situation, and step-by-step ways to get your fish eating again. The advice is simple, beginner-friendly, and applies to most freshwater aquariums, with notes for specific species where needed.
Is Not Eating Always Bad?
Normal fasting can happen
Some fish skip meals when they are new, stressed, or adjusting to your routine. It is common for a new fish to refuse food for 1 to 3 days after moving to a new tank. Many fish will also eat less if you just changed their environment, cleaned the filter, or rearranged decor. As long as the fish is otherwise active and not showing disease signs, short fasting is usually normal.
Night feeders and shy fish
Many bottom dwellers and shy species eat after lights go out. Corydoras, plecos, some loaches, and many catfish prefer dim light. If you only feed during bright daytime, you may think they are not eating. Try feeding in the evening, dim the room, or use a small night light so you can observe. Place sinking foods where these fish actually hang out, such as under wood or near caves.
Temperature and seasons
Fish metabolism depends on temperature. If the water is too cool, tropical fish slow down and may refuse food. Conversely, if it is too hot, oxygen drops and stress rises, also lowering appetite. Some species (goldfish, koi) naturally eat less in cooler seasons. Make sure your tank stays within the correct range for your species.
Breeding, mouthbrooding, and guarding behavior
Fish that are guarding eggs or fry may stop eating to protect the nest. Mouthbrooding cichlids carry eggs or babies in their mouths and often do not eat during that time. This can last 1 to 3 weeks and is normal. Observe calmly; do not force-feed.
Quick Triage: What To Do Today
Pause and avoid overfeeding
Do not keep dumping food in hoping the fish will finally eat. Uneaten food rots and makes water toxic. Offer a tiny amount, watch for 3 to 5 minutes, and remove leftovers with a net or siphon. Many healthy fish can safely fast for 2 to 7 days, depending on species and size.
Test water right away
Use a liquid test kit for ammonia, nitrite, nitrate, and pH. If ammonia or nitrite is above 0 ppm, or nitrate is above 40 ppm, appetite will drop. Write the numbers down. High readings point to water quality as the cause and must be corrected before worrying about diet.
Do a large water change
Perform a 30 to 50 percent water change using dechlorinated, temperature-matched water. This instantly reduces toxins and can revive appetite within hours. Always treat tap water with a conditioner that removes chlorine and chloramine.
Increase oxygen and surface agitation
Add an airstone or raise the filter output to ripple the surface. Low oxygen makes fish sluggish and uninterested in food. You cannot “over-aerate” with simple aquarium air pumps, so more bubbles are usually helpful.
Observe for disease signs
Look closely for spots, fuzzy patches, clamped fins, rapid gill movement, swollen bellies, stringy white poop, flashing (rubbing on objects), or gasping at the surface. Note any behavior changes: hiding, lethargy, hanging near the surface or bottom, tilting, or spinning. These clues guide next steps.
Reduce stress
Dim the lights, add a background to the tank, and provide hiding places with plants, rocks, or wood. If you see bullying, use dividers or move aggressive tank mates. Feed small amounts in multiple spots so shy fish can eat without competition.
Quarantine if needed
If a fish looks sick, move it to a separate hospital tank with a heater, filter, and air. Bare bottom tanks make it easier to keep clean and monitor waste. Treating in quarantine protects the main tank and makes dosing more accurate.
Water Quality Problems That Kill Appetite
Ammonia and nitrite: the top appetite killers
Ammonia and nitrite burn gills, stress the fish, and often lead to refusal to eat. Healthy levels are 0 ppm for both. Spikes happen in new tanks, during filter changes, after overfeeding, or when you clean the filter too aggressively. Fix by doing large water changes, adding bottled beneficial bacteria if needed, and feeding less until readings stabilize.
Nitrate: slow stress over time
Nitrate builds up in mature tanks. Keep it below 20 to 40 ppm for most freshwater fish. High nitrate causes stress, weakens the immune system, and reduces appetite. Regular water changes, live plants, and avoiding overstocking help control it.
pH, KH, and GH swings
Sudden changes in pH stress fish and affect appetite. KH (carbonate hardness) stabilizes pH. If KH is very low, your pH can crash, making fish feel unwell. Test your source water, and keep parameters stable. Do not chase exact numbers unless your species requires it; aim for consistency.
Chlorine, chloramine, and heavy metals
Untreated tap water contains chemicals that harm gills and gut bacteria. Always use a water conditioner that neutralizes both chlorine and chloramine. If your fish refuse food after a water change, suspect untreated water or a big temperature mismatch.
Temperature mismatches
Keep a reliable thermometer in the tank. Most tropical community fish prefer 24 to 27°C (75 to 81°F). Bettas do well at 26 to 28°C (79 to 82°F). Goldfish prefer cooler water, around 20 to 23°C (68 to 74°F). Rapid drops or increases can shut down appetite. Make changes slowly, 1 to 2°C per day.
Flow and oxygen
Stagnant water has low oxygen, especially in warm tanks. Strong water flow also helps, but too much flow can stress species like bettas. Balance the current for your fish. Surface agitation is key to gas exchange; you should see gentle ripples across the top.
Filter care and cycling
A well-cycled filter hosts bacteria that convert toxic ammonia to safer nitrate. Do not rinse filter media under tap water; it kills beneficial bacteria. Instead, swish in a bucket of tank water. Replace media only when it falls apart, and never all at once. If your tank is new or recently cleaned, appetite loss may be part of “new tank syndrome.” Be patient and keep feeding very light while the cycle stabilizes.
How to change water safely
Match new water temperature to within 1°C (2°F). Dose dechlorinator for the full volume of new water. Vacuum the substrate to remove waste, especially in tanks with messy eaters like goldfish and cichlids. Refill slowly to avoid shocking fish. After the change, run extra air for an hour.
Stress Factors That Suppress Appetite
New environment and acclimation
Moving fish is stressful. Float the bag to match temperature, and drip or cup-acclimate to match pH and hardness if needed. Lights should be off for the first day. Offer a tiny feeding on day two. Many fish settle within a few days.
Tank size and crowding
Overstocking causes constant stress and competition. Fish may hide or be chased away from food. Use realistic stocking guidelines and upgrade tank size if fish outgrow their space. Provide shelters so weaker fish can retreat.
Bullying and incompatible tank mates
Some species nip fins, guard territories, or dominate food. Watch at feeding time. If one fish scares others from the food, feed on both sides of the tank or use feeding rings. In severe cases, rehome the bully or rearrange the decor to break territories.
Lighting and cover
Bright lighting with no plants or decor leaves fish exposed and nervous. Add floating plants, fine-leaf plants, or caves. Use a dark background. Keep lights on a timer for a stable photoperiod, about 6 to 8 hours for low-light planted tanks or 8 to 10 hours for non-planted tanks.
Noise and vibrations
Loud speakers, slamming doors, tapping on glass, and heavy foot traffic can frighten fish. Place the tank in a calm spot. Teach kids not to tap on the glass. Keep hands out of the tank unless needed.
Handling and nets
Chasing fish with a net or frequent catching can cause days of stress. Use a container to gently scoop fish, and minimize handling. Keep maintenance calm and steady.
Food type, size, and quality
Hard, oversized pellets can be hard to swallow. Old or stale food loses smell and taste. Try smaller pellets, crush flakes for tiny fish, or pre-soak sinking pellets. Rotate foods for variety and better nutrition. Store dry food in a cool, dry place and replace every 6 months after opening.
Feeding timing and competition
Some fish learn feeding times. Feed at the same times daily. For mixed tanks, feed surface fish first with floating food, then feed sinking foods for bottom dwellers. Offer multiple small feedings so everyone gets a chance.
Disease and Parasites That Cause Appetite Loss
External parasites: Ich and velvet
Ich looks like tiny white grains of salt. Velvet looks like a fine golden dust. Both cause scratching, clamped fins, and low appetite. Treat in quarantine if possible. Raise temperature gradually if your species tolerates it, increase aeration, and use a suitable medication as directed. Remove carbon during treatment and complete the full course even if fish look better.
Gill flukes and heavy breathing
Flukes damage gills, causing gasping, flashing, and refusal to eat. Fish may hang near the surface or filters. Medications with praziquantel are commonly used. Ensure high oxygen during treatment. Confirm with a vet if possible.
Internal parasites and worms
Stringy white or clear poop, weight loss despite interest in food, and intermittent eating suggest internal parasites. Common treatments include praziquantel, levamisole, or metronidazole depending on the parasite. Feed medicated food when possible to target the gut. Quarantine helps prevent spreading.
Bacterial infections
Red sores, ulcers, fin rot, or a swollen belly can be signs of bacterial disease. Often appetite drops early. Clean water is essential. In severe cases, antibiotics may be needed, best used in a hospital tank under guidance and with careful dosing.
Constipation and bloat
Overfeeding dry pellets without soaking, or feeding lots of high-protein foods to herbivores, can cause constipation. Signs include swollen belly, stringy feces, and hovering. Skip feeding for 24 to 48 hours, then offer blanched peas for suitable species (not for strict carnivores), soaked pellets, or fiber-rich foods. For African cichlids and goldfish, reduce high-protein treats and add more veggie content.
Swim bladder issues
Fish that float, sink, or tilt may have swim bladder problems from stress, infection, or diet. Fasting for a day, feeding soaked pellets, reducing currents, and improving water quality can help. If infection is suspected, a targeted medication may be needed.
Fungal issues
White cottony patches can be fungus or secondary to injury. Appetite usually drops. Keep water clean, isolate if needed, and use a suitable antifungal treatment if confirmed. Remove carbon and increase oxygen during treatment.
When to use salt or medications
Aquarium salt can help with mild stress or some external parasites in many freshwater fish, but avoid or dose carefully with scaleless fish like loaches, corydoras, and some catfish, and never use salt in planted shrimp tanks. Copper-based treatments can harm invertebrates and some fish. Always research your species, follow directions, and never mix medications unless directed by a vet.
Feeding Fixes That Work
Use foods that trigger appetite
Offer frozen or live foods to spark interest: bloodworms, brine shrimp, daphnia, blackworms, and mysis shrimp are common choices. For herbivores, try blanched spinach, zucchini, or spirulina-based foods. Garlic-soaked food can help some fish start eating; use it as a short-term tool, not a daily habit.
Match the food to the species
Herbivores and algae grazers need plant-based foods and graze often. Carnivores prefer meaty foods and may eat fewer, larger meals. Omnivores do well with variety. Surface feeders like hatchetfish prefer floating foods; mid-water fish like tetras take slow-sinking foods; bottom dwellers need sinking wafers or pellets. Plecos need wood and algae wafers; corydoras prefer small sinking pellets and frozen foods.
Size, texture, and soaking
Offer bite-sized food. If pellets are too hard, pre-soak for a few seconds so they soften and sink. Gel foods are excellent for picky fish and allow you to mix in medication when needed. For tiny fish or fry, crush flakes or use micro-pellets and powdered foods.
Plan the feeding schedule
Feed small amounts once or twice a day for most species, only what they finish in 2 to 3 minutes. For grazers, add a small vegetable clip or wafer that stays in the tank for a few hours. Skip one feeding per week to prevent digestive issues in many community fish.
Keep the tank clean while tempting
When trying rich foods to tempt appetite, remove leftovers quickly. Use a turkey baster or siphon to spot-clean the substrate. More frequent small water changes help keep water stable while you experiment.
Freshness and storage
Dry foods lose nutrients and smell after opening. Buy small containers and replace every 6 months. Keep lids tight and store in a cool, dry place. Thaw frozen foods in a cup of tank water and avoid pouring in the packing juices, which can add excess nutrients.
Species Notes for Picky Eaters
Betta fish
Bettas often prefer small floating pellets and frozen foods. Many refuse flakes. Keep water warm and calm, and avoid strong currents. If a betta stops eating after a move, dim lights and try offering one or two pellets at a time. Remove any food that sinks and is ignored.
Goldfish
Goldfish are messy and need high filtration and frequent water changes. They may stop eating when ammonia or nitrite rises. Use sinking, veggie-rich pellets to reduce gulping air at the surface. Blanched peas can help if they look bloated, and avoid pellets that expand a lot in water.
Cichlids, including African and Discus
African cichlids can suffer bloat if fed too much protein. Use spirulina-based foods and high water movement with strong oxygenation. Discus need warm, clean water and often prefer frozen foods. Both groups can be territorial; feed in multiple spots and provide cover.
Plecos and other catfish
Many plecos are mostly herbivores and need vegetables and algae wafers. Wood is essential for some species. Night feeding works best. Corydoras like soft, small sinking foods and prefer cooler, well-oxygenated water. If they are not eating, check for high nitrate and low oxygen.
Tetras, barbs, and livebearers
Community fish often eat better in groups. Schooling reduces stress. Livebearers like guppies and mollies appreciate some salt tolerance but do not require salt if water is stable. Stringy white feces in livebearers may mean internal parasites; consider quarantine and appropriate treatment.
Shrimp and snails
While not fish, they are part of many tanks. Copper medications can kill them, and some fish foods contain copper as a trace element. Keep water clean and stable. If shrimp stop eating, check for copper exposure, sudden parameter shifts, or overfeeding causing poor water quality.
Step-by-Step Troubleshooting Plan
Day 1: Stabilize and observe
Test ammonia, nitrite, nitrate, and pH. Do a 30 to 50 percent water change with dechlorinated, temperature-matched water. Increase aeration. Offer a tiny amount of the fish’s preferred food and remove leftovers. Turn down lights and reduce noise. Watch behavior for 10 minutes.
Day 2: Adjust environment
If ammonia or nitrite is not zero, do another water change and reduce feeding to almost none. Add hiding spots and a background. Try feeding at dusk or after lights go off for shy fish. Offer a different food type, such as frozen brine shrimp or a smaller pellet.
Day 3: Check temperature and flow
Set temperature to the species’ preferred range. Improve surface agitation if gill movement is fast or fish linger at the top. If you suspect bullying, observe at feeding time and feed in multiple locations or separate fish.
Day 4: Consider disease
Look again for spots, frayed fins, swelling, or odd feces. If symptoms point to parasites or infection, move the fish to quarantine and begin an appropriate, species-safe treatment. Remove carbon during medication and increase aeration.
Day 5: Reassess feeding strategy
Try a different format: gel food, thawed frozen, or soaked pellets. For bottom dwellers, place food near their shelters. Keep portions tiny and siphon leftovers after 10 minutes.
Day 6 to 7: Monitor and maintain
Keep testing water every other day until stable. Continue small water changes if nitrate stays high. Once the fish eats reliably, slowly return to a normal feeding schedule and routine maintenance.
Prevention: Make Appetite Loss Rare
Quarantine new fish
Set up a small hospital tank for new arrivals for 2 to 4 weeks. Observe, feed, and treat if needed before adding to the main tank. This prevents parasites from entering your display tank and keeps stress low for everyone.
Test regularly and log results
Check ammonia, nitrite, nitrate, and pH weekly at first, then at least monthly once your tank is mature. Keep a simple notebook or phone log. Trends help you catch problems early and explain appetite changes.
Stable maintenance routine
Do consistent water changes, typically 25 to 40 percent weekly for most community tanks. Clean the substrate and gently rinse filter media in old tank water. Avoid big, sudden changes that shock fish.
Feed quality, varied foods
Rotate between pellets, flakes, frozen, and, when safe, occasional live foods. Use species-appropriate foods. Small portions keep water clean and fish eager for meals. Replace old food often.
Backup equipment and power
Have spare air pumps, heaters, and dechlorinator on hand. Power outages can crash oxygen and temperature, leading to appetite loss or worse. A battery-powered air pump is a simple, lifesaving tool.
Conclusion
Bring appetite back by fixing the root cause
Fish stop eating for three big reasons: water quality problems, stress, and disease. Start with the basics: test water, change water, add air, and reduce stress. Offer the right food at the right time and place, tailored to the species. If you see disease signs, move the fish to quarantine and treat carefully. Most fish will return to normal feeding once the environment is stable and they feel safe. With a simple routine and a watchful eye, you will turn a worrying situation into a quick recovery and keep your aquarium healthy for the long term.