Fish treats: what can you safely give your fish?

Why treats matter - and why most fishkeepers overdo them

Treats serve a genuine purpose. They add dietary variety, trigger natural foraging behaviour, and can improve condition and colour in fish that eat a monotonous flake-only diet. Bloodworms before a breeding attempt, daphnia to relieve mild constipation, or a piece of blanched courgette for your pleco - these are real, practical uses.

The problem is that "treating" your fish quickly becomes overfeeding. Fish don't have a satiety signal the way mammals do. They will eat until there's nothing left, then stress-eat more if you keep dropping food in. Meanwhile, every uneaten morsel is converting to ammonia in your tank. Most water quality crashes in otherwise healthy tanks come back to overfeeding, and a lot of those overfeeding incidents start with enthusiastic treat sessions.

So the framework here is: treats are a supplement to a complete diet, not a reward system for you to enjoy watching. Keep that distinction clear and you'll use them well.

The best treats by fish type

Not every treat suits every fish. Feed the wrong thing to the wrong species and you're either wasting food, creating a water quality problem, or in some cases genuinely harming the fish.

Carnivores and insectivores (bettas, cichlids, most tetras, rainbowfish)

Frozen bloodworms (Chironomus larvae) are the go-to for most carnivorous fish. They're protein-dense, widely available, and accepted by virtually every fish that eats animal matter. Buy frozen rather than live if you're buying from a store you're not 100% confident in - freezing kills most pathogens and parasites that live food can carry.

Brine shrimp (Artemia sp.) are lower in protein than bloodworms but excellent for variety. Adult frozen brine shrimp work well for medium fish; newly hatched brine shrimp (baby brine, or BBS) are one of the best first foods for fry and small species like microrasboras or chili rasboras. Hatching your own BBS is straightforward and far cheaper than buying frozen portions repeatedly.

Daphnia is worth keeping in rotation. It's low-calorie, high in fibre relative to other live or frozen foods, and acts as a mild laxative - genuinely useful if your fish look bloated or constipated after a spell of dry food. Most community fish and bettas take it readily.

Tubifex worms are popular but carry a real disease risk if sourced from the wild or from unverified suppliers. Freeze-dried tubifex is lower risk but also lower nutrition. Skip them unless you have a trusted, clean source.

Omnivores (most community fish, goldfish, guppies, mollies)

Omnivores handle a wider range of treats. All the frozen options above work, plus:

Gel foods are underrated. You can buy commercial gel food bases or make your own by blending ingredients (leafy greens, seafood, spirulina, garlic) with gelatine or agar. The result is a high-moisture, balanced food with no preservatives that most fish accept readily. It's particularly good for fish that struggle with pellets or flake.

Blanched vegetables work for most omnivores and all herbivores. Courgette (zucchini), cucumber, and spinach are the common choices. Blanch or briefly microwave them to soften the cell walls, let them cool fully, then clip or weigh them down so they sink. Remove whatever's left after a few hours.

Herbivores and algae-eaters (plecos, otocinclus, mollies, many cichlids)

These fish genuinely benefit from vegetable treats. A diet of just algae wafers is fine but limited. Rotate in:

• Blanched courgette, cucumber, or broccoli florets
• Blanched kale or spinach (in small amounts - high oxalate content means don't make it a daily staple)
• Slices of raw sweet potato or butternut squash - these are dense enough to sink without clipping
• Nori (unseasoned dried seaweed sheets) - clip to the glass for open-water grazers like mollies

Bottom dwellers and scavengers (corydoras, loaches, shrimp)

Corydoras and loaches are often assumed to live on whatever falls to the substrate - and while they'll hoover up scraps, they still need deliberate feeding. Sinking wafers and pellets are their staple, but for treats: frozen bloodworms, daphnia, and blanched vegetables all work. Drop them in after lights out if your loaches are nocturnal and getting outcompeted at feeding time.

Shrimp (cherry, amano) aren't fish but they're in most community tanks. They'll eat almost anything - algae wafers, blanched veg, small pieces of snowflake mushroom. Avoid copper-containing foods entirely; copper is acutely toxic to invertebrates at concentrations fish tolerate without issue.

Foods you should never feed your fish

Most of the "foods to avoid" lists online are obvious, but here are the ones people actually try:

Bread. It swells massively in the gut, has no nutritional value for fish, and clouds water fast. People feed it because fish gobble it up - fish also gobble up polystyrene beads if you drop them in. Appetite is not a measure of nutritional suitability.

Raw chicken or beef heart. Some old-school cichlid keepers swear by beef heart for large carnivores. It's not without precedent - you can find it in some prepared cichlid foods - but raw supermarket meat carries salmonella and other bacteria, and the fat content in mammalian meat is structured differently to the fats in fish and invertebrates. Your fish can't process it efficiently. If you want a high-protein meaty treat for large cichlids, use frozen fish-based foods or whole frozen prawns instead.

Human snack food - crackers, crisps, cereal. Salt, additives, and seasoning will stress fish and degrade water quality. There's no upside.

Feeder goldfish (for predatory fish like oscars or large cichlids). This is a hobbyist debate, but the science is clear enough: feeder fish from pet stores are frequently diseased, poorly conditioned, and nutritionally deficient. They're a reliable disease vector. Use frozen silversides or frozen whole prawns instead - safer, more nutritious, and easier to store.

Waxworms and mealworms. Sometimes suggested as reptile crossover treats. Too high in fat for regular use and the chitin in mealworm exoskeleton is hard for fish to digest. Occasional use with large predatory fish is unlikely to cause immediate harm, but there's no good reason to use them over purpose-made fish foods.

How often and how much

One to two treat feedings per week is the right range for most tanks. Some experienced fishkeepers go higher - particularly those running species-specific setups with predatory fish that need protein variety - but for a community tank, once a week is plenty and leaves less room for error.

Portion size is the harder variable to get right. The commonly cited "two-minute rule" (feed what's eaten in two minutes) is a reasonable proxy, but it's not a guarantee. Some fish eat fast and still leave substrate-level scraps. The honest rule is: watch where the food lands and check the substrate after the feeding session. If you're finding uneaten pieces after five minutes, you fed too much.

After any treat feeding - especially frozen food, which releases liquid as it thaws - check your parameters over the next 24-48 hours. If ammonia or nitrite ticks up, you either fed too much or your tank isn't fully cycled and your biological filtration can't handle the load. Understanding your nitrogen cycle properly will tell you exactly why this happens and what your filter is doing with the waste.

Live food: the benefits and the risks

Live food - live brine shrimp, daphnia, blackworms, wingless fruit flies - triggers feeding responses that frozen food doesn't always match. For fish that are reluctant feeders, or for conditioning fish before spawning, live food is hard to beat.

The risk is disease. Live food from unreliable sources is one of the most common ways parasites and bacterial infections enter a tank. Culture your own where possible (brine shrimp and daphnia are both easy to culture at home), or source from suppliers who test their livestock. If you buy from a pet store, look at the condition of the tank the live food is kept in. Dirty, cloudy water with dead organisms floating is a bad sign.

Blackworms (Lumbriculus variegatus) deserve a special mention. They're excellent conditioning food and most fish go berserk for them, but they need to be kept refrigerated in clean, frequently changed water. Old blackworms in stagnant water will crash your tank. Keep them only if you're committed to maintaining them properly.

What most guides miss: treat feeding and water quality

The connection between treat feeding and water quality is real and underappreciated. Even a single generous bloodworm feeding in a tank with a small biofilter can produce a measurable ammonia spike within 12 hours. In a heavily stocked tank or one with a newer filter, that spike can stress fish.

The solution isn't to avoid treats - it's to understand your tank's margins. If you're already at the upper end of your stocking capacity, your filter is already working close to its limit. Treat feeding needs to be more conservative, and a water change in the 24 hours after a heavy treat session is smart practice.

Tracking parameters consistently - before and after treat sessions - is the quickest way to understand how your specific tank handles the extra load. App-aquatic's test log lets you record readings over time so you can actually see the pattern rather than guessing. Check your target parameter ranges if you're not sure what you're looking for.