Aquarium fish food guide: flakes, pellets, live food, and common mistakes

Overfeeding is the number one cause of death in home aquariums. Above diseases, above water chemistry errors, above species incompatibilities. An overfed fish produces waste that raises ammonia, which stresses the fish, which destroys the tank's biology, which kills. It is a simple cycle and one that beginner aquarists consistently underestimate.

But underfeeding or feeding the wrong thing is equally destructive. A malnourished fish develops bacterial infections, loses its colouration, and has a shortened lifespan. Between too much and too little, between generic supermarket flakes and species-appropriate nutrition, there is a world of difference that this guide covers in full.

French version available: Nourriture pour poisson d'aquarium.

Understanding fish nutritional needs

Not one diet for all

The first mistake is treating all aquarium fish as a single nutritional category. Needs vary radically depending on three parameters: water type (tropical freshwater, cold freshwater, marine), natural dietary regime (carnivore, herbivore, omnivore), and mouth size and morphology.

Tropical freshwater: the most common fish in hobby aquariums. Tetras, guppies, platies, cichlids, discus, corydoras, loaches, plecos. Needs vary enormously by species.

Cold freshwater: primarily goldfish (Carassius auratus), veiltail, shubunkins. Slower metabolism, lower protein requirements, sensitive to temperature fluctuations.

Marine: reef fish (clownfish, surgeonfish, damsels) and non-reef marine fish. High protein requirements, extreme sensitivity to water quality, often more complex feeding requirements.

Protein requirements by dietary regime

Fish type	Examples	Protein requirement	Main source
Strict carnivore	African cichlids, Oscars, Arowana	45-55 percent	Invertebrates, fish
Opportunistic carnivore	Tetras, guppies, platies	35-45 percent	Mixed invertebrates + plant
Omnivore	Corydoras, goldfish	28-38 percent	Balanced mix
Herbivore	Pleco, Tropheus, spirulina cichlids	28-35 percent (plant)	Algae, vegetables

Carnivorous African cichlids like Mbuna need protein-rich animal-based food. But some herbivorous cichlids like Tanganyika's Tropheus die from a condition called "bloat" if given excess animal protein - their digestive system is simply not adapted for it. Feeding the same food to all your cichlids is a potentially fatal mistake.

Similarly, plecostomus (Hypostomus plecostomus) is often sold as a universal "algae eater". It is an herbivore with plant protein requirements around 30 percent that needs wood to gnaw for digestion. A diet based on standard tropical flakes - too high in animal protein - weakens it over time.

Cold vs tropical water: metabolism and feeding frequency

A goldfish in an 18°C tank has a significantly slower metabolism than a guppy in a 26°C tropical tank. Digestion is slower, caloric requirements are lower. Feeding a goldfish with the same frequency and quantity as a tropical fish inevitably leads to overfeeding.

General guidelines:

Tropical fish (22-28°C): 2 times per day, small quantities
Cold water fish (16-20°C): once per day, reduced quantity
Marine fish: depends on species, generally twice per day

Species-specific feeding profiles

Understanding the broad categories of carnivore, herbivore, and omnivore is a starting point. Species-level feeding profiles reveal the real complexity.

Betta splendens: the obligate micro-carnivore

The betta (Betta splendens, or Siamese fighting fish) is one of the most commonly kept fish in the world and one of the most frequently misfed. Its natural diet in the wild consists almost entirely of insects, insect larvae, and small crustaceans at or near the water surface.

Bettas are strict carnivores with a short digestive tract optimised for animal protein, not plant matter. Key feeding facts:

Protein requirement: 40-50 percent minimum, animal-source only
Feeding frequency: 1-2 times per day, very small quantities (4-6 pellets maximum per meal)
Fasting day: one day per week is strongly recommended - bettas are prone to constipation and swim bladder issues linked to overfeeding
Food format: floating micro-pellets or freeze-dried bloodworms and daphnia. Generic tropical flakes are not appropriate - they sink too quickly and contain too much plant protein
Foods to avoid: any food with plant proteins as a primary ingredient, spirulina-based flakes, vegetables

The most common betta feeding mistake is overfeeding. A betta's stomach is roughly the size of its eye. Four pellets is a meal. The betta begging behaviour at the glass front is not hunger - bettas beg constantly regardless of satiety because their predatory instinct responds to movement above the water surface.

Carassius auratus: the goldfish omnivore

Goldfish are omnivores with a metabolism directly tied to water temperature. This makes them uniquely sensitive to feeding errors across seasons.

Protein requirement: 30-38 percent, mix of animal and plant sources
Temperature dependency: above 18°C, feed once or twice daily. Between 10-18°C, feed every 2-3 days. Below 10°C, stop feeding entirely - goldfish cannot digest food at low temperatures and will develop potentially fatal gut impaction
Food format: floating pellets (goldfish that swallow air with food at the surface develop swim bladder issues - some aquarists prefer gel food or sinking pellets to reduce this risk)
Key nutrients: goldfish specifically benefit from carotenoid-rich foods (spirulina, marigold extract, astaxanthin) for colour enhancement

Fancy goldfish varieties (veiltails, orandas, bubble-eyes) have compressed body shapes that make them more prone to swim bladder disorders. These varieties benefit from gel food or briefly soaked sinking pellets rather than floating food, to minimise air ingestion.

Hypostomus plecostomus: the misunderstood herbivore

The common pleco is sold in virtually every pet shop as a "tank cleaner" and is one of the most routinely underfed fish in the hobby. Several critical points that contradict common practice:

A pleco is herbivorous with 80-85 percent of its natural diet consisting of biofilm, algae, and decomposing wood. It is not a general waste eater
Wood is not optional enrichment - it is a dietary necessity. The cellulose from driftwood provides substrate for the intestinal bacterial flora that allows plecos to digest their plant-heavy diet. A pleco tank without driftwood will develop digestive problems
Animal protein needs: 10-15 percent of total diet. Occasional offerings of frozen bloodworms or sinking carnivore pellets prevent deficiency
Primary food: spirulina wafers, vegetable wafers (cucumber, courgette, spinach, raw peas), algae sheets. Blanch hard vegetables briefly for easier processing
Protein to avoid: high-animal-protein tropical flakes as the primary diet will weaken the pleco's immune system over 6-12 months through chronic protein overload relative to digestive capacity

Plecos grow very large (30-50 cm for common varieties) and produce substantial waste. They are often bought for small tanks at a young age and quickly overwhelm the biological filtration. Feeding appropriately means managing waste output - another reason to feed plant matter (lower waste load) rather than high-protein foods.

Cichlidae: the most diverse feeding family

The cichlid family spans five continents and includes species ranging from strict herbivores to apex predators. Feeding a cichlid tank correctly requires species-level research, not a generic "cichlid food" approach.

African Rift Lake cichlids (Mbuna, Peacocks, Haplochromids):

Mbuna are strict herbivores (algae grazers in the wild) - feed spirulina-based flakes and vegetable matter. Animal protein above 10-15 percent of diet causes Malawi bloat, a fatal digestive condition
Peacock and Haplochromid cichlids are insectivores and small fish predators - 45-50 percent protein, cichlid pellets plus frozen invertebrates
Never keep strict herbivores and carnivores in the same tank with the same feeding regime

South American cichlids (Oscars, Discus, Angels, Eartheaters):

Oscars are opportunistic carnivores requiring 45-50 percent protein. Feed cichlid pellets plus feeder crickets, earthworms, and occasional frozen fish. Do not feed "feeder goldfish" - they carry disease and create a thiamine deficiency through the enzyme thiaminase
Discus have the most complex feeding requirements of any common aquarium fish: 45 percent protein, heavy reliance on frozen bloodworms and artemia, water temperature strictly 28-30°C. Discus are often not recommended for beginners precisely because of their sensitivity to both food quality and water parameters
Angelfish are omnivores accepting a wide range of foods but do best with 35-40 percent protein and regular supplementation with live or frozen brine shrimp

Types of aquarium fish food

Flakes

Flakes are the most widespread and convenient food. They float at the surface and gradually disperse through the water column, allowing surface and mid-water feeders to eat.

Advantages:

Convenient, long shelf life (12-18 months sealed)
Wide variety of formulas (tropical, goldfish, herbivore, carnivore)
Affordable price
Easy to portion

Disadvantages:

Not suitable for bottom-dwelling fish (corydoras, loaches, plecos)
Break down quickly in water if uneaten
Nutritional quality varies enormously by brand
Can lose some of their vitamins after opening (oxidation)

Best use: surface and mid-water feeders in a standard community tank (tetras, guppies, platies, mollies, danios).

Pellets

Pellets come in several formats: floating, sinking, and semi-floating. The format must match the fish's typical swimming position.

Floating pellets: for surface feeders such as African cichlids, Oscars, and cold water fish like goldfish. They allow you to observe feeding and adjust quantity accordingly.

Sinking pellets: for bottom dwellers. Essential for corydoras, loaches, plecos, and all fish that naturally feed on the substrate. Flakes rarely reach the bottom in sufficient quantity in a planted tank.

Advantages of pellets:

Better water stability (less rapid dissolution)
Often higher nutritional density than flakes
Mouth-size appropriate formats available
Less water pollution when consumed promptly

Tablets and wafers

Tablets (or wafers) are specifically formulated for bottom-dwelling herbivores. Spirulina tablets for plecos and compressed vegetable wafers (courgette, spinach) are essential supplements for strict herbivores.

Plecos need wood to gnaw (driftwood in the tank) not only for enrichment but for digestion: cellulose from wood serves as a substrate for their intestinal bacterial flora. Wood and algae-based tablets complement this requirement.

Freeze-dried food

Freeze-drying preserves the nutrients of live food without the pathogen risks. Freeze-dried tubifex, daphnia, bloodworms, shrimp - these are excellent protein supplements, particularly for:

Stimulating fish before breeding
Varying the diet of carnivores
Enriching the diet of difficult species

Important: freeze-dried foods should be rehydrated before feeding, especially for small-stomached fish. A dry tubifex cube absorbing water inside a fish's stomach can cause digestive problems.

Frozen food

Frozen foods (bloodworms, brine shrimp, daphnia, shrimp, mussels) offer the best nutritional value after live food, with fewer risks. They are particularly suited to:

Discus (nutritionally demanding)
Marine carnivorous fish
High-protein cichlids
Fish in breeding condition

Storage: maximum 6 months in the freezer. Never refreeze after thawing. Thaw in a small amount of tank water before feeding.

Live food

Live food (fresh brine shrimp, live bloodworms, live daphnia, insects) stimulates hunting instincts, enhances colouration, and optimises breeding. It is particularly valuable for species that are difficult to feed in captivity.

Risks to manage:

Possible vector for diseases and parasites (bloodworms in particular)
Delicate storage requirements
Live brine shrimp require a hatchery

Freshly hatched brine shrimp nauplii (Artemia salina) are the safest and most nutritious live food for fry and small fish. See our species food guide for recommended live food sources.

The best brands rated

Grade A: the references

Brand	Flagship product	Score	Type	Strength
Hikari	Hikari Micro Pellets	A (88/100)	Pellets	Scientific formula, digestibility
New Life Spectrum	NLS Thera-A	A (86/100)	Pellets	Colour enhancement, quality proteins
Sera	Sera Vipan	A (83/100)	Flakes	Wide range, consistent quality

Hikari (88/100) is the Japanese reference in global aquaristics. Each product is formulated for a specific category: Hikari Cichlid Gold for cichlids, Hikari Sinking Pellets for bottom dwellers, Hikari Marine-A for marine fish. Formulas are developed in collaboration with fish nutrition researchers and their ingredients are publicly documented. Hikari is the aquarium equivalent of Acana in canine nutrition.

New Life Spectrum (86/100) is an American brand that revolutionised ornamental fish nutrition by prioritising nutritional density and colour enhancement. The Thera-A range contains garlic and medicinal plants for immune support. NLS is particularly renowned for improving discus and cichlid colouration.

Sera (83/100) is a German brand with 60 years of experience in aquaristics. Its range covers all categories (flakes, pellets, tablets, freeze-dried) with consistent quality. Sera Vipan is the standard tropical community tank flake reference.

Grade B: good value for money

Brand	Product	Score	Comment
Tetra	TetraMin Flakes	B (72/100)	Widely available, acceptable quality
JBL	JBL NovoBel	B (69/100)	Reliable German brand, complete range
Tropical	Tropical Supervit	B (67/100)	Polish brand, good value

Tetra is the most widely available brand in the UK and Europe (garden centres, general pet shops, supermarkets). Their TetraMin is acceptable for a beginner community tank but lacks the nutritional density of grade A brands.

What to avoid: generic brands

Supermarket own-brand flakes and no-name brands systematically score lowest in our database. Recurring characteristics:

Unknown-quality fish meal as the primary protein source
Artificial colourants to simulate an appealing appearance
Vitamins degraded by poor storage
No documentation on actual composition

The price difference between a generic flake and Hikari or Sera is approximately £2-3 for a month of feeding a standard tank. It is the least justified corner to cut in aquaristics.

The 2-minute rule: the golden rule of fish feeding

The most important rule in fish nutrition: only feed what your fish will consume in 2 minutes maximum.

Why 2 minutes?

Any food not consumed after 2 minutes begins to decompose in the water. This decomposition is bacterial and produces ammonia (NH3). Ammonia is directly toxic to fish from 0.02 mg/L according to studies on acute toxicity in freshwater (ECHA). The nitrogen cycle (ammonia - nitrites - nitrates) is the foundation of aquarium chemistry, and overfeeding systematically disrupts it.

How to apply the rule

Give a small quantity (less than you think is needed)
Watch whether everything is consumed within 2 minutes
If yes and fish are still actively seeking food, add a second small quantity
Stop as soon as fish slow down or ignore the food
Remove uneaten food with a pipette or gravel vacuum after each feeding

Removing uneaten food is particularly important in tanks with fine substrate (sand) where waste accumulates between grains.

Weekly fasting days

Experienced aquarists generally recommend one fasting day per week. This is not neglect - it is beneficial practice:

Allows the fishes' digestive systems to rest
Reduces nitrate accumulation
Encourages fish to clean up small leftovers in the tank
Reduces constipation risk in sensitive species (veiltails, lionheads)

Common mistakes and how to avoid them

Mistake 1: giving the same food to all fish in the tank

A typical community tank often contains surface feeders (guppies), mid-water feeders (tetras), and bottom dwellers (corydoras). Giving only flakes does not properly feed the corydoras and loaches. Always supplement with sinking pellets or tablets for the bottom. This is one of the most persistent errors in community tank keeping - the bottom feeders are invisible during feeding and their malnutrition goes unnoticed until it becomes disease.

Mistake 2: feeding on a fixed schedule without observing

Fish needs vary with temperature, season (for species sensitive to photoperiod), and reproductive cycle. In winter, a goldfish in an outdoor pond or unheated tank should stop being fed below 10°C - it can no longer digest properly. A goldfish fed at 8°C will have food rotting in its digestive tract for days, causing septic peritonitis.

Mistake 3: using old flakes

Vitamins in dry foods oxidise after opening. A pot of flakes opened more than 3 months ago has lost a significant portion of its vitamin content. Vitamin C (ascorbic acid) is the most rapidly degraded. Deficiency symptoms include pale colouration, sluggish behaviour, fin deterioration. Buy smaller containers rather than large economy tubs you cannot finish in time. Store in a cool, dark place - light and heat accelerate oxidation.

Mistake 4: confusing "herbivore" with "vegetarian"

A pleco is herbivorous but needs small amounts of animal protein (10-15 percent of diet). A Tropheus cichlid is a strict herbivore - too much animal protein causes bloat. Research the specific needs of each species before choosing their food. "Herbivore" in fish nutrition does not mean "never any animal protein" - it means plant matter is the dominant energy source, but species-specific requirements vary.

Mistake 5: neglecting iodine and trace elements in marine aquariums

Reef fish have iodine, manganese, and other trace element needs that dry foods rarely cover at 100 percent. Supplement with frozen foods and marine-specific supplements. Marine nutrition is significantly more complex than freshwater.

Mistake 6: feeding feeder fish to carnivorous species

Feeder goldfish are a long-standing practice for large carnivorous fish (Oscars, Arowanas, large predatory cichlids). This practice carries two documented risks. First, feeder goldfish raised in crowded conditions are disease vectors - they introduce ich, internal parasites, and bacterial pathogens at high rates. Second, goldfish and other cyprinids contain the enzyme thiaminase, which breaks down thiamine (vitamin B1) when consumed. A diet consisting primarily of feeder goldfish causes chronic thiamine deficiency, leading to neurological symptoms and early death. Use earthworms, crickets, krill, or appropriately-sized frozen fish as safer and more nutritious alternatives.

Mistake 7: stopping medication before the full course

This is strictly a feeding-adjacent mistake that affects many aquarists. When treating a disease with medicated food or water-column medication, stopping treatment when the fish "looks better" is a major error. Fish show clinical improvement 2-4 days before the pathogen is actually eliminated. Stopping early creates partial treatment, which may lead to antibiotic resistance in bacterial pathogens and relapse within 7-10 days. Always complete the full prescribed course.

Mistake 8: not accounting for tank population dynamics at feeding time

In a competitive community tank, dominant fish eat first and subordinate fish are consistently underfed. This is particularly common in tanks with size disparities or strong hierarchies (cichlid tanks, goldfish tanks with size-mixed populations). The solution: spread feeding across multiple locations in the tank simultaneously, and observe which individuals are actually eating. If a fish is not seen eating over several days, it is likely being outcompeted.

Food type comparison table

Type	Best for	Shelf life	Water pollution	Nutritional value	Price
Flakes	Surface/mid-water	12-18 months (sealed)	Medium	Good if grade A brand	Low
Floating pellets	Surface/mid	18-24 months	Low	Very good	Medium
Sinking pellets	Bottom	18-24 months	Low	Very good	Medium
Tablets/wafers	Herbivore bottom fish	12 months	Low	Good	Medium
Freeze-dried	Supplement	24 months	Low	Very good	High
Frozen	Carnivores, discus	6 months (frozen)	None	Excellent	Medium-high
Live	Fry, difficult species	Days/weeks	None	Excellent	Variable

See our complete fish food ranking to view all rated brands from A to E.

Feeding fry

Fry have specific requirements that adult foods cannot meet.

First days: livebearer fry (guppies, platies, mollies) have a yolk sac that provides nutrients for 24-48 hours. Do not feed immediately after birth.

First feeding: extremely fine powdered food (infusoria, hard-boiled egg yolk powder, specialist fry foods like Hikari First Bites). Standard flakes are too large for fry mouths.

Brine shrimp nauplii: the optimal food for rapid growth. From 3-5 days depending on species size. Set up a simple hatchery (water bottle, air pump, salt, brine shrimp eggs) for fresh nauplii.

Frequency: fry eat 4-6 times per day (rapid small metabolism). Split the adult portion into several micro-meals or use a fine-tuned automatic feeder.

The 5 rules to remember

Match food to species: herbivore, carnivore, omnivore, surface feeder, bottom feeder - every fish has specific needs
2-minute rule: only feed what is consumed within 2 minutes
2 meals per day for tropicals, 1 for cold water fish, 0 below 10°C for cold water species
Vary the diet: base flakes + sinking pellets for the bottom + freeze-dried or frozen supplements 2-3 times per week
Choose grade A or B brands: Hikari, Sera, New Life Spectrum. The difference in monthly cost is negligible. The difference in fish health over 5 years is not

For the full range of rated products including species-specific recommendations, see our fish food rankings and ingredient encyclopaedia.

Sources

Boyd CE. "Water Quality Management for Pond Fish Culture." Elsevier, 2019. https://www.elsevier.com/
Stickney RR. "Aquaculture: an introductory text." CABI Publishing, 2005.
ECHA (European Chemicals Agency). "Ammonia aquatic toxicity data." https://echa.europa.eu/
Watanabe T. "Importance of Docosahexaenoic Acid in Marine Larval Fish." Journal of the World Aquaculture Society, 1993.
National Research Council. "Nutrient Requirements of Fish and Shrimp." National Academies Press, 2011. https://www.nationalacademies.org/
Hikari Aquatic Research. Formulation studies and digestibility data. https://www.hikari.info/
Dabrowski K, Ciereszko A. "Ascorbic acid and fish reproduction." Aquaculture Research, 2001.

Sophie Lefevre, Species Nutrition Specialist, PetFoodRate