Why Are My Fish Not Eating?

Seeing a fish ignore food can be worrying. Maybe they used to rush to the glass at feeding time, and now they swim away. Or maybe a new fish has never eaten since you brought it home. The good news is this problem is common, and most cases have simple fixes. In this guide, I will walk you through how to figure out why your fish are not eating, what to check first, how to adjust water and feeding, and when to worry about disease. Everything here is beginner-friendly and practical so you can help your fish feel better and start eating again.

First, Understand What Is Normal

New Fish Often Skip Meals

It is normal for newly purchased fish to refuse food for a few days, sometimes up to a week. Transport, new water chemistry, new tank mates, and bright lighting can shock them. Give them time to settle, keep the lights dimmer, offer small amounts of easy foods like frozen brine shrimp, and avoid crowding the front glass. If water quality is good and there are no illness signs, patience is your best tool.

Shy or Nocturnal Feeders

Some species mostly eat at night or when the tank is quiet. Many catfish, loaches, plecos, and some knife fish feed after lights out. If you only feed during the day, they may never get to it. Try feeding after the room is dark and the fish room is quiet, or add a small late-evening feeding. If possible, switch to dim “moonlight” for 30 minutes before full darkness to encourage natural behavior.

Species That Naturally Fast

Healthy fish can fast for short periods. Mouthbrooding cichlids may not eat while holding eggs. Wild-caught fish can take days to accept prepared foods. Bettas and some gouramis will occasionally skip a meal. One missed feeding is not an emergency. Watch overall behavior and body condition rather than a single feeding event.

Do Not Overfeed to Compensate

When fish refuse food, many people offer more and more types at once. That often makes water quality worse and stress higher. Offer small amounts, give them space, and focus on fixing the cause rather than pushing more food.

Water Quality: The Number One Appetite Killer

Test the Water and Know Your Targets

Even if the water looks clear, invisible toxins can suppress appetite within hours. Test ammonia, nitrite, and nitrate right away. Ammonia and nitrite should be 0 ppm. Nitrate should be preferably under 20–40 ppm for most community fish. If ammonia or nitrite are detectable, reduce feeding, do a 30–50% water change with dechlorinated water, and make sure your filter is working well and not clogged.

If your tank is new or recently cleaned too thoroughly, it may be “cycling” and unable to process waste. In that case, fish often stop eating due to stress. Use a good water conditioner that detoxifies ammonia and nitrite temporarily, add bottled bacteria if you have it, and feed very lightly until readings stabilize at 0 ammonia and 0 nitrite.

Temperature Matters More Than You Think

Cold water slows fish metabolism and appetite. Too warm can stress them and reduce oxygen. For most tropical community tanks, aim for about 75–78°F (24–26°C). Bettas like around 78–82°F (26–28°C). Goldfish do better cooler, around 64–72°F (18–22°C), depending on variety. A simple digital thermometer is essential. Sudden changes of more than 2–3°F (1–2°C) can also stop feeding, so adjust slowly.

Oxygen and Water Movement

Low oxygen makes fish listless and uninterested in food. Signs include rapid gill movement, hanging near the surface, or staying by filter outflows. Increase surface agitation with an airstone or raise your filter output to ripple the surface. Avoid overly strong currents for species that dislike flow, but ensure there is enough gas exchange. Proper surface movement greatly improves appetite within a day or two.

Chlorine, Chloramine, and Other Toxins

Always use a dechlorinator when adding tap water, and make sure it handles chloramine, not just chlorine. Even small amounts of chlorine can burn gills and shut down feeding. Residual cleaning products, aerosol sprays near the tank, or soap on your hands can also cause appetite loss. Wash hands with water only before tank work, and never use soap inside the aquarium.

Stress From the Environment

Bullying and Territorial Pressure

Fish under constant attack stop eating. Watch for fin nipping, chasing, or one fish guarding a corner. During feeding, check if dominant fish scare others away from food. The fix might be as simple as adding a second feeding spot, spreading the food more widely, or rearranging decor to break up territories. In serious cases, separate the bully or add more hiding places to reset hierarchies.

Too Much Light and Reflections

Bright lights can alarm fish, especially new ones. Turn down intensity, reduce photoperiod during acclimation, or feed during a dimmer time of day. Strong reflections on the glass can make fish think an intruder is present. Placing a background on the back and sides of the tank, or reducing light hitting the glass, helps many fish relax and eat.

Not Enough Hiding Spots

Security boosts appetite. Add plants (live or artificial), caves, driftwood, and rockwork so fish can break line of sight and feel safe. A comfortable fish in a well-structured aquascape is far more likely to eat in front of you.

Sudden Changes Shock Fish

Large, fast water changes with big temperature or pH swings can stop feeding. Try to match temperature and avoid drastic chemistry shifts. When possible, do moderate, regular water changes rather than infrequent large ones. Stability is as important as hitting perfect numbers.

Food Problems You Can Fix Today

Wrong Type or Size of Food

Fish often refuse food that is the wrong size or texture. Tiny tetras struggle with large flakes or big pellets. Bottom-dwellers ignore floating food. Carnivores may not recognize veggie pellets at first, and herbivores can develop bloat on high-protein diets and stop eating. Match the food to the species and mouth size. Crush flakes for small fish, use micro-pellets for nano fish, and choose sinking wafers for bottom feeders.

Sinking vs. Floating and Feeding Zones

Many fish feed at a certain level. Surface feeders like hatchetfish prefer floating foods. Midwater fish do well with slow-sinking micro-pellets. Catfish and loaches need sinking wafers. If multiple species share the tank, offer different foods at once to reach all levels. This reduces competition and ensures shy fish get a chance to eat.

Stale or Off Food

Fish can smell old food and refuse it. Vitamins degrade quickly in flakes and pellets once opened. Store dry food in a cool, dry place, ideally refrigerated, and replace it every 6 months. If you opened a large tub months ago and fish have grown picky, try a fresh container. You may be surprised how quickly they resume eating.

Variety That Wakes Up Appetite

Some fish lose interest in the same meal every day. Rotate between high-quality pellets or flakes, frozen foods like brine shrimp or daphnia, and occasional live foods from a safe source. Frozen options are often an easy win for picky eaters because they smell strong and look natural. Always thaw frozen foods in a small cup of tank water before feeding and do not overdo rich treats like bloodworms.

Health Issues That Suppress Appetite

External Parasites: Ich and Velvet

White spot disease (ich) appears as tiny white grains of salt on the body and fins. Velvet looks like a dusty gold or rusty sheen and often causes clamped fins and flashing. These parasites stress fish, making them stop eating. Typical treatments include raising temperature carefully for tropical fish (not goldfish) and using a targeted medication following label directions. Remove carbon from filters during treatment and keep oxygen high.

Internal Worms and Protozoa

Signs of internal parasites include weight loss despite available food, long white or clear stringy feces, and poor appetite. Some common treatments include praziquantel for certain worms, metronidazole for protozoa, and levamisole for nematodes. Always confirm compatibility with your species and follow product instructions. If several fish show these signs, treat the whole tank or move fish to a quarantine tank for easier dosing.

Bacterial Infections and Mouth Injuries

Look for red or swollen areas, fuzzy patches, ragged fins, or damaged mouths. A torn mouth from fighting or rough decor can make eating painful. If the mouth looks injured, offer softer foods like thawed brine shrimp and keep water ultra-clean to promote healing. For bacterial issues, targeted antibacterial meds or clean-water management may be needed. Remove sharp decorations if fish are injuring themselves while feeding.

Bloated Belly and Swim Bladder Trouble

Constipation and bloat cause fish to lose appetite. Overfeeding dry food that expands in the gut is a common cause. Try fasting the fish for 24 hours, then offer shelled peas for suitable species or a small portion of thawed daphnia. Avoid puffed-up or pineconed scales, which can indicate dropsy (a serious condition often tied to organ failure or infection). If pineconing is present, act quickly with clean water, isolation, and appropriate treatment advice.

A Simple Step-by-Step Troubleshooting Plan

Step 1: Test water for ammonia, nitrite, nitrate, and check temperature. Fix anything out of range. Aim for 0 ppm ammonia and nitrite, low nitrate, and a stable temperature suitable for your fish.

Step 2: Increase oxygen and reduce stress. Add surface agitation, dim the lights, reduce noise around the tank, and provide hiding spots.

Step 3: Offer the right food in the right place. Match size and type. Try a small amount of thawed frozen brine shrimp or daphnia for a few days to kick-start appetite. Feed tiny portions to avoid polluting the water.

Step 4: Watch for signs of bullying or fear. Feed at multiple spots, use sinking and floating foods, and consider rearranging decor. If one fish is aggressive, separate temporarily.

Step 5: Observe for illness. Check the body, fins, gills, eyes, and feces. Look for spots, dust, redness, swelling, or worms. If you see clear symptoms, choose a suitable medication and follow directions carefully.

Step 6: Give it time but set limits. A healthy adult fish can go several days without food, but if a new fish still refuses to eat after 3–5 days with good water and zero stress, try different foods and feeding times. If an established fish stops eating for more than 48–72 hours and shows other symptoms, escalate to health checks and possible treatment.

Feeding Techniques That Work

Target Feeding for Shy or Bottom Fish

Use a feeding cone or a turkey baster to deliver food to specific fish. For catfish and loaches, drop sinking wafers near their hiding places after lights go off. For midwater shoals, scatter micro-pellets across the current so all fish get a chance. The goal is to get food in front of the right mouths without conflict.

Routine and Training

Fish learn habits. Feed at the same times each day. Turn off the filter briefly during feeding so food does not shoot away, then turn it back on after a few minutes. Step back from the glass and keep movement calm while they investigate. If your presence scares them, try staying still or feeding with the room light dimmed.

Appetite Boosters Used Safely

Garlic extract or foods that contain garlic can help some picky fish start eating, and soaking pellets in tank water for a minute softens them. Do not soak in tank water for too long or nutrients leach out. Avoid using strong additives or human foods. Many fish respond best to high-quality frozen options for a few days, then transition back to pellets or flakes once the habit forms.

Species-Specific Tips

Betta Fish

Bettas often refuse old pellets or pellets that are too large. Choose a small, high-protein betta pellet and feed 2–4 pellets per meal, twice daily, with one fast day weekly. Keep temperature around 78–82°F (26–28°C). Avoid strong currents; a calm surface encourages feeding. If a betta refuses dry food, offer thawed brine shrimp or daphnia for a couple of days, then mix in pellets once they are eating.

Goldfish

Goldfish need cooler, oxygen-rich water and produce a lot of waste. Poor water quality quickly kills their appetite. Use sinking pellets to reduce gulping air at the surface, which can cause buoyancy issues. Offer blanched veggies like spinach or zucchini and gel foods formulated for goldfish. Keep temperature around 64–72°F (18–22°C), and perform regular large water changes. Fancy varieties are sensitive to sudden changes and strong currents.

Plecos and Other Catfish

Many plecos eat wood, algae, and veggies more than meaty foods. If your pleco is not eating, add driftwood and offer algae wafers or blanched vegetables at night. Corydoras prefer small sinking foods and will ignore floating flakes. Avoid sharp substrates for corys and keep them in groups so they feel secure enough to feed.

African Cichlids

Mbuna and other herbivorous cichlids can suffer from bloat if fed too much protein or fatty foods. Use spirulina-based pellets and veggie-heavy diets. Keep water hard and alkaline, with stable pH in the high 7s to low 8s. Overcrowding and hierarchy disputes often suppress appetite; provide plenty of rockwork and multiple food drop points.

Tetras, Rasboras, and Small Community Fish

Small schooling fish prefer tiny foods that sink slowly. Micro-pellets and crushed flakes work well. Strong flow can blast food out of reach and make feeding stressful. Keep them in groups of their own species so they feel safe enough to eat at the front of the tank.

Discus and Sensitive Species

Discus and other delicate fish stop eating with even minor water quality issues. Keep temperature warm and stable, around 82–86°F (28–30°C), and maintain very clean water with frequent changes. Offer high-quality frozen foods and soft pellets, and avoid sudden changes in pH or TDS. A quiet environment helps a lot.

Common Mistakes That Keep Fish From Eating

Feeding Too Much, Too Often

Leftover food rots, raising ammonia and lowering oxygen. That creates a spiral of stress and lower appetite. Feed what they can finish in about 1–2 minutes, then stop. If there is leftover food on the bottom, remove it with a siphon.

Cleaning Filters the Wrong Way

If you rinse filter media under tap water with chlorine, you kill helpful bacteria and crash your cycle. Rinse filter media in a bucket of tank water instead. A crashed cycle means ammonia spikes and fish refuse food.

Skipping Quarantine for New Fish

New fish can bring parasites or bacteria that spread and make everyone eat less. Whenever possible, quarantine new fish in a separate tank for 2–4 weeks. Observe eating behaviors, treat if needed, and only then move them to the main tank.

When to Worry and Seek Help

Red Flags That Need Fast Action

Watch for rapid breathing, lying on the bottom or gasping at the surface, pineconed scales, large wounds, worms protruding from the vent, or heavy white spots. If you see these signs plus refusal to eat, move quickly. Improve water quality, increase oxygen, and start appropriate treatment or ask for help from an experienced aquarist or aquatic veterinarian.

How Long Is Too Long Without Food?

Healthy adult fish can often go several days to a week without food, but young fish and very small species need frequent meals. If a new fish refuses food for more than 5–7 days, or an established fish stops eating for 48–72 hours and looks unwell, act on the troubleshooting plan, test water, and consider targeted treatment.

Preventing Future Feeding Problems

Make Stability Your Priority

Keep a consistent routine. Test your water weekly, do regular partial water changes, and avoid big swings in temperature or pH. Feed a balanced diet with variety and store foods properly. Comfortable fish are confident eaters.

Set Up the Tank for Comfort

Use a background, add plants and hardscape, and create zones so shy fish can eat away from boisterous tank mates. Adjust flow and lighting to suit the species. The more your tank matches their natural needs, the better they eat.

Keep Good Records

Write down water test results, foods offered, and behavior changes. Patterns will emerge. You might notice that appetite dips after long gaps between water changes, or that a certain food always goes uneaten. Simple notes help you solve problems faster next time.

A Quick Case Example

The New Tetra School That Would Not Eat

A beginner adds a group of neon tetras to a bright, new tank. They ignore flakes and stay in a corner. Testing shows 0.25 ppm ammonia; the tank is still cycling. The aquarist uses a conditioner that detoxifies ammonia, adds more plants for cover, dims the light, and feeds a tiny amount of micro-pellets and thawed brine shrimp in the evening. Within three days, ammonia reads 0, the tetras school in the open, and they start eating confidently.

The Pleco That Ignored Pellets

A common pleco in a bare tank will not eat algae wafers. The keeper adds a piece of driftwood, offers wafers after lights out, and places a slice of blanched zucchini near the pleco’s cave. Appetite returns the same week.

Conclusion

Fish stop eating for a reason, and it is usually not a mystery once you break it down. Check water quality first. Make sure temperature and oxygen are right. Reduce stress with dimmer lights, hiding spots, and a calm routine. Match the food to the species, size, and feeding zone, and refresh old food if needed. If illness signs appear, act promptly and treat appropriately. With a steady hand and simple changes, most fish regain their appetite quickly. Keep observing, stay patient, and remember that stability and comfort are the foundation of healthy, hungry fish.