• 0.2 mm particle size - the buying decision on this page. Nothing else in the frozen range goes small enough for a first-feeding mouth.
• Whole animals - flash frozen intact rather than minced into a slurry, so what enters the tank is a discrete particle a polyp can capture.
• Single-ingredient declaration - rotifers and nothing else. No binder, no added colour, no preservative named.
• Feeds the animals nothing else reaches - small-polyp corals, feather dusters, nudibranchs and jellyfish are all too small-mouthed for a copepod.
• Freezer stable, no culture to maintain - the practical alternative is a live rotifer culture, which needs daily attention and can crash without warning.
• Pre-portioned cubes - press out one cube and the rest of the blister goes straight back in the freezer.
• 91.5% moisture - a soft, easily dispersed particle rather than a hard fragment.

Particle size is the only thing that matters when the animal being fed has a mouth measured in fractions of a millimetre. This table places rotifers against the other single-species frozen foods so you can match food to mouth rather than guess.

Fry outgrow rotifers quickly. Most keepers move up a size class within the first few weeks, which is why a 100 g blister is usually the right quantity rather than a bulk pack.

Full ingredient declaration

Reproduced exactly as Ocean Nutrition publishes it: Rotifers.

That is the complete declaration. Rotifers are not crustaceans or molluscs, so this is one of the few frozen aquarium foods with no shellfish allergen in it. No artificial colours, preservatives, ethoxyquin, BHA or BHT are named, because nothing beyond the animal itself is named at all.

Analytical constituents

Ocean Nutrition does not publish a crude fibre figure for this product, so none is shown here rather than estimated.

Why the wet figure looks low

Frozen foods are analysed wet. Only 8.5% of this cube is solid matter, the rest is water.

Dividing the published protein by that solid fraction puts frozen rotifers at roughly 69% protein on a dry-matter basis. The 0.7% ash is the lowest in the range, which is consistent with an animal that has no shell to speak of.

Ocean Nutrition's direction is to feed 2 to 5 times a day, offering only what the tank will clear within five minutes. With fry, frequency matters more than quantity - small amounts often beats one large feed.

Press out one cube into a small container and let it defrost at room temperature for ten to fifteen minutes. Do not thaw the whole blister.

Mix the thawed cube with a little tank water and deliver it with a pipette or syringe, close to the fry or the polyps. A 0.2 mm particle broadcast into open water is gone into the filtration before anything finds it.

Turn off the return pump, wavemakers and skimmer for five to ten minutes while feeding. This is not optional advice with a particle this small - a running skimmer will strip most of the feed out of the water before a coral captures it.

Keep the blister frozen and never refreeze a portion that has thawed.

Suitable for

• Marine fish fry at first feeding, and delicate fry that cannot handle larger prey
• Shrimp larvae and other small crustacean larvae
• Small-polyp stony corals, and non-photosynthetic corals that feed on suspended particles
• Anemones, feather dusters, tube worms, nudibranchs and jellyfish
• Seeding food into a new reef tank, or supporting a refugium population

Not suitable for

• Adult fish of any size as a staple - the particle is too small to be worth their effort
• Fry that will only take moving prey - frozen rotifers do not swim, and some marine larvae will not strike at a motionless particle. Where that is the case a live culture is the only answer, and no frozen food substitutes for it
• Use as a sole diet for growing fry beyond the first weeks - move up a size class as the mouths grow
• Freshwater aquariums - Ocean Nutrition rates this one for marine fish and invertebrates
• Automatic feeders, which cannot handle a frozen wet food
• Feeding with the skimmer running, which removes most of it before anything eats it

• Frozen Red Plankton Flat 454g - the next size class up, for fry that have outgrown 0.2 mm.
• Ocean Nutrition frozen copepods - a mid-size particle to bridge rotifers and adult foods.
• Ocean Nutrition frozen invertebrate food - a blended invertebrate diet for the same filter feeders.
• Ocean Nutrition Coral Pellets Small 100g - a shelf-stable coral food for days the freezer stays shut.
• Ocean Nutrition Brine Shrimp Eggs (Box) - for hatching live nauplii when fry need moving prey.

Aquarium foods carry no manufacturer warranty period. Your rights under the Australian Consumer Law apply in full and sit in addition to anything a manufacturer offers, including a remedy if a product arrives thawed, damaged or not of acceptable quality.

This is a frozen product and is handled as cold-chain stock. It travels by in-store pickup or local delivery rather than standard parcel post, because a blister that thaws in transit cannot be refrozen.

How big are Ocean Nutrition frozen rotifers?

Ocean Nutrition publishes an animal size of 0.2 mm, making them the smallest food in its frozen range. That size is the entire reason to buy them - they reach fry, shrimp larvae and small-polyp filter feeders that cannot take a copepod or a daphnia.

Can frozen rotifers replace a live rotifer culture?

For filter feeders, corals and many fry, yes, and they remove the burden of maintaining a culture that can crash overnight. For marine larvae that will only strike at moving prey, no - a frozen rotifer does not swim, and in that situation a live culture or freshly hatched brine shrimp is the only workable option.

Should I turn the filtration off while feeding?

Yes, for five to ten minutes, and the skimmer especially. A 0.2 mm particle is exactly the size a protein skimmer is designed to remove, so feeding with it running sends most of the food to the collection cup instead of the livestock.

How do I feed rotifers to corals rather than the fish?

Mix the thawed cube with a little tank water and deliver it directly onto the polyps with a pipette, syringe or turkey baster while circulation is off. Broadcasting into open water feeds whichever fish reaches it first.

How long can fry live on rotifers alone?

Rotifers are a first food rather than a complete grow-out diet, and most fry outgrow the 0.2 mm size class within the first few weeks. Move up to a larger particle as soon as the fry are physically able to take one, rather than waiting for growth to stall.

Do rotifers contain shellfish allergens?

Rotifers are not crustaceans or molluscs, and Ocean Nutrition declares rotifers as the sole ingredient, so no shellfish allergen appears in the declaration. That makes this an unusual exception among frozen aquarium foods, most of which are crustacean-based.