What Do Small Fish Eat? A Detailed Look at Their Diverse Diets

As an aquarium hobbyist I’m always fascinated by the eating habits of small fish. Their diets are extremely varied depending on habitat species, and food availability. Knowing what small fish eat helps me provide a balanced diet and proper care.

In this comprehensive guide, we’ll explore the dietary preferences of small fish in freshwater, saltwater, and wild environments.

Common Food Sources for Small Fish

Small fish consume a diverse range of foods including:

• Phytoplankton – Microscopic, plant-based organisms like algae and diatoms. A staple for many herbivorous fish.

• Zooplankton – Tiny animal organisms like copepods, rotifers, and krill. A vital protein source.

• Insects – Larvae, nymphs, adult aquatic insectsImportant for insectivores

• Crustaceans – Shrimp, amphipods, isopods, and other small crustaceans. High in nutrients.

• Annelids – Worms like tubifex, bloodworms, blackworms. Offer live or frozen.

• Detritus – Decaying organic matter. Provides energy.

• Aufwuchs – The algae coating on plants, wood, rocks. Grazed by some fish.

• Small fish – Fry, fingerlings and juvenile fish. Mainly for predatory species.

• Pellets/flakes – Formulated fish feeds. Staple of captive fish.

As you can see, small fish eat a huge variety of foods. Next, let’s look at some specific examples.

Herbivorous Small Fish Diets

Herbivorous fish subsist mainly on plant matter. Here are some examples:

• Goldfish – Aufwuchs, algae, aquatic plants, prepared foods.

• Cichlids – Algae, phytoplankton, vegetable matter, some insects.

• Tetras – Algae, plant debris, phytoplankton, insects, worms.

• Livebearers – Algae, detritus, vegetable debris, small invertebrates.

• Danios – Algae, phytoplankton, plant matter, small insects.

Though plant foods form the bulk of their diet, most herbivorous fish will also opportunistically eat meaty foods for protein. This makes them omnivorous rather than solely herbivorous.

Carnivorous Small Fish Diets

Carnivorous fish thrive on animal-based foods. Some examples include:

• Bettas – Insects, brine shrimp, bloodworms, daphnia, small crustaceans.

• Killifish – Insects, worms, crustaceans, zooplankton, small fish.

• Rainbowfish – Insects, crustaceans, annelids, zooplankton, fish fry.

• Loaches – Insect larvae, small snails and crustaceans, worms.

• Pufferfish – Snails, clams, crustaceans, shellfish, fish, worms.

Though carnivorous, they may graze on some vegetable matter and aufwuchs too. Carnivorous fish need high protein foods for optimal growth and health.

Omnivorous Small Fish Diets

Many small fish are opportunistic omnivores, consuming both plant and animal matter. Some examples:

• Minnows – Insects, zooplankton, algae, plant debris.

• Rasboras – Insects, worms, shrimp, phytoplankton, plant matter.

• Barbs – Insects, worms, aufwuchs, zooplankton, vegetation.

• Guppies – Insect larvae, worms, aufwuchs, algae, plant debris.

• Mollies – Algae, plant debris, insects, worms, crustaceans.

• Platies – Algae, plant matter, brine shrimp, worms, small crustaceans.

Omnivores adapt well to varied diets and changing food availability in the wild. In aquariums, they need a balanced flake/pellet diet along with supplemental meaty foods.

Saltwater Small Fish Diets

Marine ecosystems offer unique food sources for small saltwater fish. For example:

• Chromis – Zooplankton, phytoplankton, marine worms.

• Clownfish – Copepods, isopods, mysis shrimp, algae, worms.

• Blennies – Detritus, benthic algae, small crustaceans, worms.

• Gobies – Aufwuchs, isopods, copepods, mollusks.

• Damselfish – Algae, plankton, small crustaceans, worms.

• Cardinalfish – Zooplankton, benthic invertebrates, marine worms.

Marine vegetation and plankton provide sustenance to small herbivorous and omnivorous species, while tiny meaty foods nurture carnivorous fish.

Small Fish Diets in the Wild

In their natural habitats, small fish feeds are largely dictated by the local environment. For example:

• Streams – aquatic insects, insect larvae, algae, aufwuchs.

• Lakes – zooplankton, phytoplankton, insects, crustaceans.

• Ponds – insects, worms, shrimp, snails, tadpoles.

• Rivers – insect larvae, shrimp, snails, algae, detritus.

• Estuaries – copepods, mysid shrimp, marine worms, mollusks.

• Coral reefs – zooplankton, benthic invertebrates, algae.

As you can see, wild small fish are adept at utilizing whatever live foods are naturally available in their habitat. Captive fish don’t have this luxury, so providing variety is key!

Common Live Foods for Small Fish

In aquariums, live foods make excellent supplemental feedings. Some top live food options include:

• Brine shrimp – Nutritious for fry and adults. Rich in protein and omega oils. Hatch shrimp eggs to culture at home.

• Daphnia – A favorite snack high in nutrients. Cold water species like whiteclouds love these. Culture daphnia yourself or purchase frozen.

• Blackworms – Loaded with protein and fats. Ideal for carnivores and fry. Can culture or buy from pet stores. Rinse well before feeding.

• Grindal worms – Tiny worms perfect for feeding small fry. Full of protein and easy to culture at home with a starter kit.

• Flightless fruit flies – Great first foods for egg layer fry like bettas and gouramis. Buy flightless cultures and feed newly hatched flies.

Live foods provide enrichment and nutrition that gets fish eagerly feeding. Introduce them slowly and in moderation to prevent bloating issues.

Diet Considerations for Small Fish Fry

Caring for tiny fry under a month old requires specialized feeding. Here are some tips:

• Start with infusoria – the microorganisms that grow in tanks. Fry nibble these naturally.

• Once free-swimming, begin feeding powdered fry starter foods multiple times a day.

• Newly hatched brine shrimp, micro worms and vinegar eels are ideal first live foods.

• Slowly introduce small live foods like daphnia, chopped bloodworms and grindal worms.

• Start offering crushed flakes and mini pellets soaked in water or gel foods.

• By 4-6 weeks old, most fry can eat standard small flake foods and micro pellets.

Proper fry feeding is vital for growth and survival rates. Offer a variety of tiny live and prepared foods several times a day in the beginning.

Best Practices for Feeding Small Fish

Now that we’ve covered what small fish eat, here are some feeding best practices:

• Provide a high quality flake or pellet as the staple diet. Look for first ingredients like fish meal, shrimp meal, spirulina.

• Complement with supplemental feedings 2-3 times per week of frozen or live meaty foods like mysis shrimp, bloodworms or daphnia. This adds valuable variety.

• Feed fry and juveniles smaller foods 3-5 times daily. Adults do well with **1