Most aquarium fish are fed a dry prepared food and do perfectly well on it. Live and frozen invertebrates are what you add when you want a fish to color up, to breed, to condition after illness, or simply to behave like a fish rather than a decoration. This guide covers which fish benefit, what the realistic options are, how much is too much, and the risks that come with feeding live. It is general fishkeeping rather than veterinary advice.
Which fish actually want insects
Not all of them. A pleco is not going to thank you for a cricket. The fish that gain most from invertebrate feeding fall into three rough groups:
- Surface and near-surface predators. Bettas, gouramis, archerfish, arowana, halfbeaks, some killifish. These take insects at the surface in the wild, and a floating terrestrial insect is a natural food item rather than a novelty.
- Small micropredators. Most tetras, rasboras, danios, small cichlids and rainbowfish. They eat small aquatic invertebrates and take live daphnia or worm cultures readily.
- Fish being conditioned. Almost any species being brought into breeding condition, or recovering from a period of poor feeding, responds to live food in a way it does not to flake.
Strict herbivores and detritivores are the exception. They are not built for a high-protein insect diet, and offering it regularly is a way to cause problems rather than solve them.
What is actually on the menu
There are two families of live food in fishkeeping and it is worth keeping them separate in your head.
Aquatic invertebrates
Bloodworms, blackworms, daphnia, brine shrimp, whiteworms, grindal worms and microworms. These are the traditional aquarium live foods, they sink or swim rather than float, and they suit the widest range of fish. Bloodworms are not worms at all: they are the larval stage of midge flies in the family Chironomidae, which is why they turn up in a discussion about insects.
Terrestrial feeder insects
This is where a feeder insect supplier is genuinely useful, and it is narrower than people expect. Terrestrial insects float, so they suit surface feeders and are wasted on anything that feeds low in the water column.
- Flightless fruit flies. The single most useful terrestrial feeder for aquarium fish. They float, they struggle on the surface film, and they are the right size for bettas, small gouramis, killifish and juvenile surface feeders.
- Small crickets. Useful for larger surface predators. Crickets come in a fine size ladder, which matters when the constraint is mouth size. We do not sell crickets. We sell dubia roaches instead, though for surface feeders the fruit flies and larvae on this list are the closer fit.
- Black soldier fly larvae. Increasingly common as a component of prepared fish feeds, and usable live for larger fish. The black soldier fly larvae guide covers their calcium content and storage.
- Mealworms. Take care here. Most of the worm feeders have a hard, chitin-heavy exoskeleton relative to their body mass, and fish digest that poorly. They are an occasional item for large predatory fish, not a routine food for a betta.
How much, and how often
The failure mode in fishkeeping is not the wrong food. It is too much of the right one, because uneaten food does not just sit there. It decays, it drives ammonia and nitrite, and the fish pays for it twice.
| Rule | Why |
|---|---|
| Feed what is eaten in about two minutes | The standard aquarium guideline. Anything still floating after that is going into the filter or the substrate. |
| Treat live and frozen invertebrates as a supplement | Common betta care guidance treats bloodworms as an occasional item, on the order of once a week rather than daily, because they are rich and easy to overfeed. |
| Remember how small the fish is | A common keeper rule of thumb is that a betta's stomach is about the size of its eye. That is the portion, and it is much less than it looks. |
| Remove what is not eaten | Within minutes, not hours. |
| Soak anything freeze-dried | Freeze-dried foods expand after being swallowed, and keepers commonly blame them for digestive trouble. |
Sizing to the fish
Fish swallow prey whole, so mouth width is the constraint and there is no getting around it.
- Match the feeder to the mouth, not to the body. A fish that looks large can have a small gape.
- Smaller and more is better than larger and fewer. Several small items are eaten and digested; one oversized item is spat out or causes a problem.
- Juveniles and fry need genuinely tiny food. Microworms, newly hatched brine shrimp and the smallest daphnia exist for this reason.
- Watch the first feed of anything new. If the fish repeatedly takes and rejects an item, it is too big or too hard.
Because feeder size names are not standardized between suppliers, a measurement is more use than a size label when you are matching a feeder to a small mouth. For roaches, the dubia roach size chart gives the length in inches behind each size name.
The risks of feeding live
This is the part that gets glossed over in most fishkeeping content, and it is the reason live food has a reputation.
Disease and parasites. Live aquatic invertebrates collected from open water can carry pathogens and parasites into a closed system. This is the specific argument for buying cultured live food from a controlled source rather than netting a pond, and it is why frozen food exists as a category: freezing removes some of that risk.
Water quality. Live foods that escape and die in the substrate are worse than uneaten flake, because they are larger and richer.
Never release anything. Live feeder cultures, aquatic plants and tank water should not go into a drain that reaches open water or into a garden pond. Non-native invertebrates establishing outside a tank is a genuine problem and it is entirely avoidable.
Nutritional imbalance. No single live food is a complete diet. Bloodworms in particular are commonly overrated: better-balanced options exist, and a fish on a bloodworm-heavy diet is not getting what a formulated food would give it.
Ordering, and where to go next
The buying pattern for aquarium keepers is small quantities of several things rather than bulk quantities of one, which is close to the opposite of how a reptile keeper buys. Two consequences follow.
Cultures make more sense than tubs for the smallest foods. Fruit flies, microworms and grindal worms are maintained as ongoing cultures rather than restocked weekly, so the buying decision is a one-off with upkeep rather than a repeating order.
For the larger terrestrial feeders, buy what will actually be eaten. A tub of crickets bought for one betta is a tub of crickets you are now keeping as pets. Feeders that store well are the practical choice, and keeping them properly rather than leaving them in the shipping container is what determines whether you use them or bin them.
Of the foods covered here, we sell fruit flies, black soldier fly larvae and mealworms, all in the feeders collection. We do not sell bloodworms or other aquatic live foods. For comparative nutrition figures on the insects, see the nutrition table in our bearded dragon feeder guide, and when an order lands, what to do when your feeders arrive covers the unpacking.
This guide describes feeding healthy fish. A fish that is bloated, has stopped eating, is producing stringy white waste, or is sitting on the bottom has a problem that a change of food will not fix, and an aquatic vet or an experienced fishkeeper is the right next step.