Every species profile says what that fish eats. This article is about the general part: how to choose a food, how much to give, and which feeding mistakes most often end in a sick fish.
Feeding type and feeding level
Fish differ not only as predators, omnivores and herbivores but also in where they eat. The mouth position gives it away:
- upturned mouth — the fish takes food from the surface (labyrinth fish, livebearers, hatchetfish);
- terminal mouth — it feeds in mid-water (tetras, barbs, rasboras);
- underslung mouth — it collects food from the bottom and from surfaces (catfish, loaches, botias).
So a community tank needs at least two foods, one floating and one sinking. Flakes are taken at the surface within half a minute and nothing reaches the bottom.
Types of food
- Dry — flakes, pellets (floating and sinking), chips, tablets for bottom dwellers. The basis of the diet: balanced and convenient.
- Frozen — bloodworm, brine shrimp, daphnia, cyclops, mysis. The best supplement to dry food: nutritious and safer than live.
- Live — the same invertebrates plus home-grown cultures (microworms, vinegar eels, fruit flies).
- Vegetable — spirulina tablets, blanched courgette, cucumber, spinach, lettuce leaves.
- Specialised — for cichlids, for discus, for shrimp, for fry.
A single food, however good, does not supply everything. Variety matters more than the brand.
How much and how often
Adult fish are fed once or twice a day, a portion they finish in one or two minutes. Anything still lying on the bottom after five minutes is no longer food but future ammonia.
- Fry and small fast-metabolism species are fed more often and less at a time — four to six times a day.
- Adult omnivores benefit from one fasting day a week.
- Large predators need only two or three meals a week: in the wild they eat rarely and much.
Overfeeding is worse than hunger. A healthy adult fish takes a week without food in its stride, while uneaten food raises ammonia within a day. The other consequence of overfeeding is fatty degeneration of the internal organs; it develops over years and cannot be reversed.
Bottom dwellers in a community tank
Catfish, corydoras and loaches usually go short in an ordinary community tank: the fish above intercept the food first. Hence the rule — sinking tablets after the lights go out, when the shoal above has settled. At least at first, check that the food really reaches the bottom: a fish with a sunken belly is starving even though "everyone gets fed".
A myth of its own is that catfish "clean the tank" and need no food. What they do not need is other fish's leftovers; a diet of their own is required by all of them.
Herbivores and protein
Mbuna, otocinclus and many loricariids graze algae off rocks in the wild. Their digestion is not built for protein: frequent bloodworm ends in bloat and death. Their diet has to be plant-based: spirulina, vegetables, foods made for herbivores.
The opposite mistake is feeding a predator vegetable flakes "for variety": it simply cannot digest them.
Live food and its risks
Live food from a natural pond is the commonest way of introducing parasites along with the meal. Frozen and home-cultured food is safer and gives up almost nothing in nutrition.
Predators do not need live feeder fish: they bring disease, and they are no better than frozen fish, prawn or pellets for predatory species. Most predators can be weaned onto non-living food, though it sometimes takes weeks.
Storage
Once opened, dry food loses vitamins, so a tub is best used up within three to six months. Keep it dark and dry, and do not tip food out with the tub held over the tank: steam gets in and the food goes mouldy.
Going away
Healthy adult fish handle a week without food better than they handle being over-fed. What works: an automatic feeder, set up before you leave and tested for a few days. What does not: "holiday blocks", which dissolve and spoil the water, and asking a neighbour to "feed them properly" — that almost always ends with the whole tub in the tank.
If a fish will not eat
Refusing food in the first days after a move is normal — that is stress. It is worrying when a fish does not eat for more than a few days, loses weight, hangs in a corner or spits food out. In that case check the water first, rather than changing the food. What to do next is in the article Fish diseases.