Goldfish flakes: are they good enough?

The tub of flakes that comes home with a first goldfish is not a mistake. Flakes have fed goldfish for generations, and a healthy single-tailed fish on a decent flake and a few vegetables can live a long life. The question is whether flakes are the best you can do, and for most fancy goldfish the answer is no.

What a flake is

A flake is made by cooking a slurry of ingredients into a thin sheet on a heated drum, then breaking the sheet into pieces. The result is extremely thin, which is what makes it float, soften quickly and take up air and moisture readily. The ingredients can be as good as those in any pellet, and on a premium flake the label reads much the same: fish or shrimp meal, wheat or oats, spirulina, vitamins. The difference is the physical form, not necessarily the recipe.

The kinds on the shelf

Flakes come in more varieties than the format suggests, and the differences are real even if the marketing overstates them.

• Standard goldfish flake. The default. A mixed-ingredient recipe aimed at general feeding, and the one most first goldfish get.
• Colour-enhancing flake, carrying carotenoids such as astaxanthin and spirulina. The mechanism is genuine — goldfish cannot make those pigments and deposit dietary ones in the skin — and the limit is that no food adds colour a fish is not genetically able to show. The pellets page covers that in full.
• Spirulina and vegetable flake, higher in plant matter and lower in protein. A reasonable part of a rotation for an adult goldfish, and closer to an omnivore’s mixed diet than a high-protein flake.
• Growth or conditioning flake, higher in protein, aimed at juveniles and at fish being brought into breeding condition. Not what an adult needs day to day.
• Pond flake, which is really a different product: larger, tougher flakes meant to hold together on open water. Indoors they are unnecessarily large.

What to read on any of them is the ingredient list rather than the front of the tub, and reading a fish food label covers the panel — including ingredient splitting, which is as common on flake tubs as on pellets.

Where flakes fall short

Three things work against flakes in a goldfish tank.

They float. A goldfish feeding at the surface tips upward and snaps at the film, and a fancy goldfish in that posture swallows air along with its food. Many keepers believe that repeated air-gulping contributes to the buoyancy problems round-bodied breeds are prone to. The link is observational rather than proven, but it is one reason this site leans toward sinking food for fancies.

They fragment. The moment a flake touches water it begins to soften and break, and once the fish start thrashing at it the fragments spread everywhere. Whatever is not eaten in the first minute drifts into the substrate and the filter, where it rots. A flake-fed tank tends to need more cleaning than a pellet-fed one.

They lose their value. The thinness that makes a flake convenient also exposes almost every part of it to air, so the fats and vitamins in it are likely to oxidise faster than in a dense pellet.

Flakes against pellets, directly

The comparison this page exists to make, in one place.

Compared on	Flakes	Pellets
Where they sit	Float, then waterlog and scatter	Available as floating, slow-sinking or sinking
Suits fancies	Poorly, because of surface gulping	Well, in a sinking form
Holding together	Break up on contact; fragments spread	Hold their shape for minutes
Portioning	Hard — a pinch varies enormously by weight	Easy — count them, or use a fixed scoop
Shelf life once open	About two months, three at most; the thin sheet takes up air and moisture readily	About two months, three at most
Small mouths	Good, crushed	Needs the right pellet size
Cost	Slightly cheaper	Slightly more, and possibly better value per useful feed

The short version: the recipes can be equally good and the format is not. A pellet is easier to measure, easier to feed where you want it, and tends to hold its nutrition longer and foul less. That is why this site treats a quality pellet as the staple and flakes as a reasonable option for single-tails, ponds and very small fish.

Sinking versus floating food

Floating food The fish tips nose-up to take food from the surface and swallows air with it. Aerophagia, the swallowing of air, is a recognised cause of buoyancy trouble in fancy goldfish.

Sinking food The fish stays level. Sinking or pre-soaked food means less air is swallowed. Soak dry food for a minute if it does not sink on its own.

When flakes are fine

Plenty of goldfish do well on flakes, and there are situations where they are the sensible choice.

Single-tailed goldfish, the commons, comets and shubunkins, are comfortable surface feeders and, keepers report, show no particular tendency to buoyancy trouble. Pond fish are usually fed floating food deliberately, because it brings them up where you can see them and lets you judge how much has been eaten; see goldfish ponds. And very small juveniles have mouths too small for most pellets, so crushed flakes are a natural early food alongside the fry foods sold for the purpose.

For an adult fancy goldfish, flakes are not harmful in themselves. They are simply a worse tool than a sinking pellet for the same job.

Feeding flakes better

If flakes are what you have, three habits remove most of their drawbacks.

Crush them. Rubbing a pinch between your fingers before it goes in produces fragments that small mouths can take and are less likely to be spat out.

Pre-soak them. Drop the pinch into a small cup of tank water, swirl for a few seconds and pour it in. Wet flakes sink slowly through the water, so the fish feed mid-water or on the bottom rather than gulping at the surface. Some water-soluble vitamin content goes into the cup, which is why an aquatic vet advises against soaking; keepers of fancy goldfish accept that as the price of food that sinks.

Measure them. A flake is so light that a pinch varies enormously. Watch what the fish finish in a minute or two, a common rule of thumb, remember what that amount looked like, and feed that. How often to feed goldfish covers the schedule; the short version is small amounts once to three times a day.

Storing them properly

Flakes are thin and take up air and moisture readily, so storage deserves particular attention here.

Never open the tub over the tank. This is a common way a tub is ruined. Warm humid air rises off an aquarium, flakes readily absorb moisture, and a tub held over the surface takes some in every time. Take it to a dry worktop, shake a portion into your hand or a lid, and close it.

Never put wet fingers in. The same problem, concentrated.

Keep it cool and dark, not on the hood. The top of a lit aquarium is a warm, bright spot, which is what oxidises fats and destroys vitamins.

Buy the smallest tub you will finish within about two months, three at most. A large tub is cheaper per gram and can be worse value, because some of it may be stale before it is used. That is likelier with flakes than with pellets.

Decant a working portion. Two or three weeks’ worth in a small airtight pot by the tank, with the main tub sealed in a cupboard. The bulk then ages at cupboard speed rather than at open-tub speed, and the small pot doubles as the portion measure — how often to feed goldfish covers why a fixed measure beats a daily judgement.

And freezing works, for a portion you want to keep longer: seal it well, freeze it, and let it come fully to room temperature before opening, so condensation does not form inside the container.

How to tell it has gone off

Three checks, and the printed date is none of them.

• Smell. Fresh fish food smells faintly marine. Sharp, sour, or like old cooking oil means the fats have gone rancid.
• Colour. Flakes fade and darken as they oxidise. A tub noticeably duller than when you opened it has lost value.
• Clumping. Flakes are hygroscopic, so clumps mean moisture has got in — which means mould is possible whether or not you can see it.

Any of the three and the tub goes in the bin. It costs very little, and rancid fat is among the recognised causes of fatty liver in aquarium fish.

What flakes do to the water

Worth its own note, because the mess is not incidental — it is a property of the format.

A flake starts breaking up the moment it is wet. Within a minute the original piece is a scatter of fragments, and the fish are chasing them rather than eating them cleanly. Whatever is not caught in that first minute drifts.

Where it drifts to: into the substrate, where it rots out of reach; into the filter intake, where it can clog the mechanical media faster than pellets do; and into the dead corner behind the decor. The cleaning guide covers getting it back out, and the thirty-seconds-a-day habit with a turkey baster is worth having in a flake-fed tank.

Two consequences to expect. A flake-fed tank may read a little higher for nitrate than a pellet-fed one on the same stocking, if more food ends up decomposing rather than eaten. And the filter sponge may need rinsing more often, which is the mechanical stage doing its job rather than a fault — goldfish filtration covers when to rinse it.

The practical mitigations are the ones already on this page: pre-soak so the food sinks together rather than scattering, feed less than feels right, and feed in one place so you can see what was missed.

Flakes for fry and juveniles

The one situation where a flake is genuinely the better tool.

Small mouths need small food, and a flake crushed to powder between finger and thumb produces particles finer than most pellets sold. That is why crushed flake has been a traditional grow-on food for goldfish fry for generations, once they are past the first week or two — feeding fry and young goldfish covers the earlier stages, where infusoria and newly hatched brine shrimp come first.

How to do it: rub the flakes to a fine powder, feed very small amounts several times a day, and siphon what is missed. Fry need frequent meals and foul water extremely quickly, and the two facts pull against each other constantly.

A growth formulation is an option here. Juveniles need about 29 to 35 percent crude protein, and some grower foods run to 40 percent or above, as the pellets page sets out: a young fish is building a body rather than maintaining one.

And move them on as the mouths grow. A juvenile that can take a fine sinking pellet is better off on one.

The false economy

Flakes look like the cheap option on the shelf and may not be, for two reasons worth spelling out.

Much of it is never eaten. A food that fragments and scatters can lose part of each meal into the substrate and the filter. Whatever that fraction is for your tank, you are buying it and the filter is processing it.

And some of the rest may go stale. A flake’s surface area means an opened tub is likely to decline faster than a pellet of the same recipe, so a large economical tub is more likely to be past its best before it is finished.

The comparison that matters is cost per useful feed rather than cost per gram. On that basis a small tub of a good sinking pellet, finished within about two months, can beat a large tub of flakes — and what keeping goldfish costs sets out why food is not where the money goes in this hobby anyway.

In a pond

Flakes are the wrong shape for outdoor feeding, which surprises people who know that floating food is right in a pond.

They blow away. A breeze takes a scatter of flakes across the surface and into the margins before the fish reach them, and a rain shower sinks them.

They break up in exactly the way they do indoors, except that here the fragments sink into a body of water you cannot siphon — goldfish ponds covers why uneaten food outdoors is a slower, larger version of the same problem.

The outdoor answer is floating pellets or sticks, which hold together, stay where they are put, and can be counted — and being able to see what has been eaten is a useful daily health check. Feeding through the seasons covers the temperature bands, including the wheatgerm foods for cool water and the point below which many keepers stop feeding altogether.

Why a flake-only diet falls short

The problem is not any single deficiency but the narrowness. A goldfish in a pond eats insect larvae, crustaceans, algae, plant fragments and detritus, a bulkier, moister and more varied diet than a dry flake. Flakes are dry, concentrated and low in fibre by comparison. Keepers report that fish fed nothing else often produce long, trailing faeces and seem more prone to constipation.

The remedy is variety rather than a different tub of flakes. Shelled peas, blanched courgette and leafy greens, described in vegetables for goldfish, add the roughage; a good pellet adds a denser, more stable nutritional base; a frozen food now and then adds interest.

Making the switch

Goldfish are conservative about food, and a fish that has eaten flakes for two years may not recognise a pellet as edible at all. Several refusals mean very little, and the method that works is gradual rather than a standoff.

• Mix, do not switch. Start with mostly flakes and a little of the new pellet, and shift the proportion over a week or two. The new food arrives among something familiar.
• Offer it first, to a hungry fish, at the start of a meal rather than after it has filled up.
• Put it where the fish will find it. A sinking pellet dropped where the flakes used to land gets investigated faster than one scattered into gravel.
• Try garlic if it is being ignored — strongly flavoured food is often accepted by reluctant eaters, and garlic is a keeper favourite, though the evidence for it is limited.
• Give it a fortnight. Two weeks of offering is a fair test.

What not to do is starve the fish into it. A day or two of light feeding alongside the offer is reasonable; a standoff is not, and it is particularly unwise with a juvenile or a thin fish — loss of appetite covers where refusing food stops being fussiness.

If you are choosing a replacement, the goldfish food buying guide compares current options, though the label-reading criteria in the pellet guide will serve you whatever the shelf holds.