Why Feeding Matters
If I had to pick the single most common reason new aquarists lose fish, it would not be disease, cycling, or water chemistry. It would be overfeeding. Uneaten food rots, rotted food becomes ammonia, and ammonia kills fish faster than almost anything else in this hobby. The neighbour who "just feeds a pinch every morning" and wonders why the water is cloudy and the fish are gasping at the surface has done this to themselves.
Feeding is also where you have the most daily control. You cannot always fix temperature, hardness, or filtration in five minutes, but you can always choose to feed less. Get feeding right and your tank stays cleaner, your fish live longer, your algae stays manageable, and your water changes actually accomplish something. Get it wrong and you will be fighting ammonia spikes, bloat, and green water for as long as you keep fish.
Here's the practical guide — the same approach I use in my own fishroom, with everything that actually matters and nothing that doesn't.
Types of Fish Food
No single food is complete. A healthy feeding rotation pulls from at least three of the categories below, and the right staple depends on the species in your tank. Here is what each one is good for, and where it falls short.
- Flakes. Cheap, common, and the default most keepers reach for. Flakes work for surface and mid-water feeders (tetras, rasborans, livebearers), but they lose vitamin potency within a few weeks of opening the tub and they crumble into dust that pollutes the water. Date your tins and replace every three months.
- Micro pellets. Better than flakes for nano fish and species under 5 cm. Pellets hold their shape, sink slowly so mid-water feeders get them, and they don't degrade as fast once opened. Hikari Micro Pellets and New Life Spectrum Nano are the two I keep on rotation. Slightly pricier than flakes but worth it.
- Frozen foods. The gold standard for variety and conditioning. Bloodworms, brine shrimp, daphnia, and mysis shrimp come in foil blister packs at any fish store. Fish go mad for them, they trigger breeding behaviour, and they are nutritionally dense. The trap is overuse — bloodworms are fatty and daily feeding causes fatty liver disease within a year. Rotate frozen in two to three times a week and always thaw in a cup of tank water first.
- Live foods. Baby brine shrimp (hatched from cysts in 24 hours), microworms, and infusoria are essential if you are breeding or raising fry, and a powerful conditioning food for adults. BBS is the single best live food — cheap, easy, and nutritionally perfect. Live food is also the only thing that works for stubborn feeders like scarlet badis and dwarf puffers.
- Algae wafers. The daily staple for bottom feeders — plecos, otocinclus, corydoras, and many shrimp. Drop one in after lights-out and remove what is left after four hours. Hikari Algae Wafers and Omega One Veggie Rounds are the reliable picks. Without these, herbivorous bottom feeders slowly starve in clean tanks.
- Vegetable matter. Blanched spinach, zucchini, and cucumber for shrimp, plecos, otos, and herbivorous fish. Blanch for 30–60 seconds, cool, cut into small pieces, and remove after four hours. This is the single most reliable way to keep otocinclus alive in a new tank where biofilm has not yet established.
- Repashy gel food. A powder you mix with boiling water, refrigerate, and cut into cubes. Stays intact in the tank for up to 12 hours without breaking down, which makes it ideal for shrimp and bottom feeders that graze slowly. A $12 jar makes months of food. Repashy Super Soil Green and Community Plus are the two I use most.
How Much to Feed
Here is the rule that fixes 90% of feeding problems: feed only what the fish can eat in 30 seconds, twice a day. If pellets or flakes are hitting the substrate before the fish eat them, you are feeding too much. If food is still floating around after a minute, net it out — it is no longer food, it is pollution.
For a typical 10-gallon community tank with 12 small fish, that works out to roughly 25–35 micro pellets per feeding, scattered across the surface so everyone gets some. For larger fish, the equivalent is a pellet or two per fish, sized to the width of the fish's eye. And fast the tank one day per week — skip both feedings. It mimics the natural lean days fish experience in the wild, aids digestion, and gives the biofilter a chance to catch up. A slightly hungry fish is always healthier than an overfed one.
Feeding Schedule by Species
Different species have radically different needs. The table below is the rotation I have settled on across the species I keep — adjust for your own mix, but the categories hold true everywhere.
| Species | Daily staple | Supplement (2–3×/week) | Notes |
|---|---|---|---|
| Tetras / rasboras / danios | Micro pellets or flakes | Frozen brine shrimp, bloodworms | Surface and mid-water feeders; fast twice a week |
| Betta | Betta pellets (3–4) | Frozen bloodworms, daphnia | Prone to bloat; skip feed one day a week |
| Livebearers (guppy, platy, swordtail) | Flakes with vegetable content | Frozen brine, blanched spinach | Need plant matter; overbreed if overfed |
| Corydoras | Sinking wafers | Frozen bloodworms, Repashy gel | Feed after lights out; they are nocturnal |
| Plecos (bristlenose) | Algae wafers + driftwood | Blanched zucchini, Repashy | Need actual wood to rasp on for digestion |
| Otocinclus | Biofilm + supplemental veggies | Blanched spinach, cucumber, Repashy | Starve without supplemental feeding in new tanks |
| Shrimp (Neocaridina / Caridina) | Biofilm + Repashy gel every other day | Blanched spinach, algae wafer fragment | Pea-sized portion; remove after 4 hours |
| Goldfish | Goldfish-specific pellets | Blanched peas (deshelled), spinach | High carb needs; tropical food causes fatty liver |
| Dwarf puffers | Live snails (essential) | Frozen bloodworms, BBS | Snails wear down the beak; without them, it overgrows |
Foods to Avoid
Some foods are not just suboptimal — they actively harm fish over time. The four below are the ones I see recommended most often by people who should know better.
- Goldfish flakes for tropical fish. Formulated for cold-water fish with higher carbohydrate and lower protein content. Tropical fish fed goldfish flakes long-term develop fatty liver disease, faded colour, and shortened lifespan. The few coins saved on goldfish food will cost you the fish within a year.
- Freeze-dried food as a staple. Freeze-dried bloodworms and tubifex are convenient and shelf-stable, but they are notorious for causing bloat — especially in bettas and goldfish. The drying process shrinks the food, the fish overeats, and the food rehydrates and swells in the stomach. Use freeze-dried as an occasional treat soaked in tank water first, never as a daily staple.
- Beefheart. A discus breeder's staple that has bled into the wider hobby. Far too rich for community fish — the fat content causes digestive issues and pollutes water faster than almost anything else. Stick to aquatic protein sources (fish, krill, shrimp, squid) that match what the fish evolved to eat.
- Human food. Bread, biscuit crumbs, rice, pasta, lunch meat — none of it. Fish cannot digest cooked carbohydrates, the food passes through them undigested, and the tank pollutes. The only kitchen items that belong in an aquarium are the blanched vegetables listed above.
Specialized Diets
Some fish have rigid dietary requirements that the standard rotation cannot meet. If you keep any of these, plan the diet before you bring the fish home — not after.
Puffers need snails. Dwarf puffers, pea puffers, and most freshwater puffers have a fused beak that grows continuously. Without hard-shelled snails to rasp on, the beak overgrows and the fish eventually cannot eat. A small snail colony (bladder snails, ramshorns, or pond snails) is not optional — it is the food that keeps the puffer alive. Feed snails at least weekly.
Otocinclus need algae and supplemental vegetables. Otos are dedicated algae grazers and they starve in clean, new, or lightly stocked tanks where biofilm has not yet built up. Supplement daily with blanched spinach, zucchini, or Repashy gel until the tank matures. A healthy oto should have a slightly rounded belly — a sunken belly is a fish that is starving.
Scarlet badis often refuse dry food. These tiny predators are wired for live prey. Many individuals never accept flakes or pellets and will simply starve next to food they do not recognise. Plan for live or frozen baby brine shrimp, microworms, and daphnia from day one. The same goes for some wild-caught celestial pearl danios and chocolate gouramis.
Crystal red shrimp need biofilm. Caridina shrimp graze constantly on the bacterial and algal film that coats surfaces in a mature tank. A new tank has no biofilm and shrimp will slowly starve even with Repashy offered daily. Mature the tank for at least two months before adding Caridina, and consider biofilm starters (powdered bacterial supplements, algal paste, leaves like catappa or guava) to seed the surfaces.
Common Feeding Mistakes
- Overfeeding. The big one. Symptoms are cloudy water, hair algae blooms, ammonia spikes after water changes, and fish with permanently bloated bellies. The fix is structural — measure the food into a small dish before feeding, not directly from the tub. If you can see food on the substrate after a minute, you have fed too much.
- Underfeeding. Rare, but it happens. Usually a keeper who has internalised the "feed less" message too hard. Symptoms are hollow bellies, lethargy, faded colour, and fish that lose weight over weeks. A healthy fish should have a slightly rounded belly, not concave.
- Feeding only one type of food. A flake-only diet leads to nutritional deficiencies — usually visible as faded colour, slow growth, or poor breeding condition. Rotate at least three foods (a dry staple, a frozen supplement, and a vegetable or live option) and you cover the nutritional bases.
- Not removing uneaten food. Food left in the tank past an hour is no longer food — it is ammonia waiting to happen. Net it out, siphon it during the next water change, or stock bottom feeders that will clean it up within minutes. I keep a small net next to every tank for exactly this reason.
Recommended Products
These are the foods and tools I keep on rotation in my own fishroom — the ones that have proven themselves across dozens of tanks and species. The first one is the single best all-round fish food I have used, and the link is an Amazon affiliate link that supports the site at no extra cost to you.
Hikari Micro Pellets
Best for: Nano fish, tetras, rasboras, small community tanks.
Slow-sinking, ingredient list leads with fish meal and krill, does not cloud the water. The single food I would keep if I could keep only one.
Algae Wafers
Best for: Plecos, otocinclus, corydoras, shrimp.
Drop one in after lights-out; remove uneaten after four hours. Hikari and Omega One are the two reliable brands.
Repashy Gel Food
Best for: Shrimp, plecos, otos, bottom feeders.
Powder + boiling water = months of food. Stays intact in the tank for 12 hours. Super Soil Green is the default shrimp pick.
If you remember nothing else from this guide, remember the 30-second rule. I have kept dozens of tanks over the years, and the difference between the tanks that run clean and the tanks that fight algae and ammonia constantly is almost always how much food goes in. Less is more. Less is always more.
Frequently Asked Questions
How much should I feed my aquarium fish?
Feed only what the fish can consume in about 30 seconds, twice a day. If pellets or flakes are hitting the substrate before the fish eat them, you are feeding too much. Fast the tank one day per week to aid digestion and reduce waste. A slightly hungry fish is always healthier than an overfed one.
What is the best food for aquarium fish?
No single food is complete. A rotation of quality flakes or micro pellets as the daily staple, frozen bloodworms or brine shrimp two to three times a week, and vegetable matter for herbivores and shrimp gives the broadest nutrition. The first ingredient on the label should be a protein source, not wheat flour or soy.
Why is overfeeding bad for aquarium fish?
Uneaten food decomposes into ammonia, which spikes water quality and stresses or kills fish. Overfeeding also causes bloat, fatty liver disease, and aggressive algae growth. More water quality problems in the hobby trace back to overfeeding than to any other single mistake. The 30-second rule exists for this reason.
Can I feed my tropical fish goldfish flakes?
No. Goldfish flakes are formulated for cold-water fish with a higher carbohydrate and lower protein profile. Tropical fish fed goldfish flakes long-term develop fatty liver disease, faded colour, and shortened lifespan. Use a tropical-specific flake or micro pellet. The few coins saved on goldfish food will cost you the fish within a year.