--- type: species title: "Golden Wonder Killifish Care Guide: Tank Setup, Diet & Tank Mates" slug: "golden-wonder-killifish" category: "freshwater" scientificName: "Aplocheilus lineatus" subcategory: "Killifish" lastUpdated: "2026-04-24" readingTime: 10 url: https://www.fishstores.org/species/golden-wonder-killifish --- # Golden Wonder Killifish Care Guide: Tank Setup, Diet & Tank Mates *Aplocheilus lineatus* Learn how to care for Golden Wonder Killifish - tank size, water parameters, feeding, compatible tank mates, and where to buy healthy fish. ## Species Overview The Golden Wonder Killifish (*Aplocheilus lineatus*) is the gold morph of the Striped Panchax, a surface-hunting predator native to standing and slow-moving freshwaters across India and Sri Lanka. The wild form wears olive-bronze flanks; the gold morph that dominates the aquarium trade looks like a polished bar of metal cruising the top inch of the tank. Hobbyists keep them for the color, the hunting behavior, and the fact that they tolerate a wider range of water conditions than most killifish in the trade. This species is often miscategorized as a beginner livebearer because of its size and shape. It is not a livebearer. It is an egg-scattering killifish with a livebearer-like build, and that single confusion drives most of the bad advice you will read about it online. | Field | Value | | ----------- | ------------------------ | | Adult size | 4 in (10 cm) | | Lifespan | 3-5 years | | Min tank | 20 gallons (long) | | Temperament | Semi-aggressive predator | | Difficulty | Beginner-Intermediate | | Diet | Carnivore (surface) | ### Natural Habitat & Origin In the wild, *Aplocheilus lineatus* sits motionless in the top few centimeters of ditches, paddy field margins, slow streams, and brackish coastal pools across southern India and Sri Lanka. Its upturned mouth and flat dorsal profile are the textbook design of a surface ambush predator. Insects landing on the water film, mosquito larvae hanging off the meniscus, and any small fish that strays into the upper zone are all on the menu. Water in these habitats varies wildly through the monsoon cycle. That is why the species tolerates the parameter swings new aquarists tend to inflict on a tank, and why it is one of the few killifish you can keep without RO water and peat-buffered tanks. ### Appearance & Color Variants The wild *Aplocheilus lineatus* shows olive flanks crossed by faint vertical bars and a row of red-edged scales. The aquarium "Golden Wonder" is a line-bred gold morph that replaces the olive base with metallic yellow-gold and intensifies the iridescent blue-green spangling along the flank. Males develop slightly longer dorsal and anal fins with red and black margins; females stay shorter-finned with a more subdued gold body. A healthy specimen at the store reflects light off every scale and holds its position just under the surface. Faded color and a body that hangs vertically near the bottom are both warning signs. ### Size & Lifespan Adults reach about 4 inches (10 cm), making them one of the larger killifish in the trade and far bigger than nano-friendly species like clown killifish. Captive lifespan runs 3-5 years with stable water and varied feeding. They grow fast in their first year - a 1-inch juvenile from the LFS is usually a 3-inch fish six months later. ## Water Parameters & Tank Requirements Golden Wonders are forgiving compared to wild-type killifish, but they still have non-negotiable requirements: surface cover, a tight lid, and enough horizontal swimming space to let them stake out a hunting position. > **Tight lid is mandatory, not optional** > > Golden Wonder Killifish are explosive jumpers. They will exit through the gap a HOB filter cuts in a glass lid, the slot for a heater cord, or the corner cutout of a stock canopy. Cover every opening with mesh, foam, or plastic strip. A carpeted floor under the tank does not save them - a 4-inch killifish on hardwood lasts about 90 seconds. ### Ideal Water Conditions A defensible target range for the species: - **Temperature:** 72-82°F (22-28°C). Room temperature is fine in most homes; a heater is only needed in cool basements. - **pH:** 6.5-7.5. Tolerates harder, more alkaline water better than most killifish. - **Hardness:** 5-20 dGH. Soft to moderately hard water both work. - **Ammonia / Nitrite:** 0 ppm. Non-negotiable. - **Nitrate:** Under 30 ppm with weekly water changes. The species also tolerates slightly brackish conditions (up to about 1.005 SG), which mirrors the coastal lagoons it occupies in southern India. Brackish is optional, not required. ### Minimum Tank Size & Layout A 20-gallon long is the practical minimum for one male and two females. Footprint matters more than volume - a 20-long (30 inches wide) gives them more usable hunting territory than a 29-gallon tall with the same water capacity. For a small group of three to five, scale up to a 29 or 40-gallon breeder. Stock the tank with floating plants. Frogbit, water lettuce, Amazon frogbit, and dense mats of Salvinia all do the job. The fish need shaded surface zones to feel secure; a bare top surface keeps them stressed and hiding behind the heater. Driftwood and tall stem plants reaching the surface fill out the look without crowding the swimming lane just below the waterline. ### Filtration & Flow Sponge filters and baffled hang-on-back filters are the standard. The goal is gentle flow - a strong return current pushes the fish out of their preferred hunting zone and constantly disturbs the floating plant raft. If you must run an HOB, point the output at the glass to break the current, or attach a piece of pre-filter sponge over the intake to slow the inflow. > **Livebearer cycle, but they are egg layers** > > Golden Wonders are often shelved at the LFS next to mollies and platies because they look similar and tolerate similar water. Do not let the shelf placement fool you into thinking you can drop them into an uncycled or two-week-old "fishless cycle gone wrong" setup. They handle nitrate swings, but ammonia still kills them like any other fish. Cycle the tank fully (zero ammonia, zero nitrite, measurable nitrate) before any fish go in. See the [aquarium cycling and setup walkthrough](/guides/20-gallon-fish-tank) for a 20-gallon-specific cycle plan. ## Diet & Feeding This is where the "predator" label earns its keep. A Golden Wonder eats anything alive that fits in its mouth - and the mouth is wider than it looks. ### Carnivore Feeding Strategy In the wild, *Aplocheilus lineatus* feeds almost exclusively at the surface: emerging insects, terrestrial bugs that land on the water, mosquito larvae, and small fry. In the aquarium, that translates to a diet built around floating foods. Sinking pellets and bottom-feeder wafers are wasted on this species - they will not chase food downward unless they are starving. Daily staple options: - **Floating carnivore pellets** - Hikari Micro Pellets, Bug Bites for small carnivores, or Northfin Krill formula - **Frozen foods** - bloodworms, brine shrimp, glassworms, mysis (thaw and float on the surface) - **Freeze-dried** - daphnia and bloodworms work, but soak first to prevent bloat ### Live Food & Enrichment Live food is where the species shines. Feeding live black worms, fruit flies (wingless *Drosophila*), small mealworms, or live mosquito larvae triggers the full ambush-and-strike behavior these fish are built for. A male in good color with live foods in the rotation looks twice as bright as one on a flake-only diet. If you have a mosquito problem in the backyard, a Golden Wonder is a 4-inch biological control system. Skim larvae from a rain barrel and drop them in - the tank will be cleared in seconds. ### Feeding Frequency & Portion Size Feed twice daily, just enough that all food is consumed within 60 seconds. Adult Golden Wonders have a full belly after surprisingly little - their stomach is small relative to body size, and overfeeding shows up fast as bloated bellies and water quality crashes in the smaller end of recommended tank sizes. > **Top-water predator - it eats anything that fits in its mouth** > > Hobbyists routinely lose neon tetras, ember tetras, chili rasboras, juvenile shrimp, and small fry of larger species the day after adding a Golden Wonder Killifish. The fish does not need to be hungry to predate - it ambushes by reflex. If a tank mate's body width is smaller than the killifish's mouth gape (roughly 1/3 of the killifish's own body length), it is food. Plan stocking around that rule, not around the fish's reputation as "peaceful." ## Tank Mates & Compatibility Golden Wonders are not community fish in the bag-of-tetras sense, but they are not solo-tank fish either. The trick is matching them with bottom and mid-column dwellers that are too large to swallow and too territorial elsewhere to bother the killifish at the top. ### Suitable Community Fish - **Corydoras catfish** - bottom dwellers, ignored by surface predators - **Larger tetras** - black skirt, congo, lemon tetras (over 1.5 inches at adult size) - **Mollies and swordtails** - share water tolerance, occupy mid-water, too big to be prey - **Peaceful barbs** - cherry barbs, gold barbs (rosy barbs work in larger tanks) - **Kuhli loaches** - nocturnal bottom dwellers that never see the killifish ### Species to Avoid - **Small nano fish** - neon and ember tetras, chili rasboras, *Boraras* species - all dinner - **Guppies and endlers** - especially fry; even adult males are at risk - **Fancy bettas** - flowing fins get nipped, and both species claim surface territory - **Other male killifish** - including other Golden Wonder males in tanks under 40 gallons - **Dwarf shrimp colonies** - juveniles will be hunted; adults may survive in heavily planted tanks For a peaceful surface-dwelling alternative if your tank stocking leans toward nano fish, the [clown killifish](/species/clown-killifish) tops out at 1.4 inches and is true community-safe. For another single-species US-native option, the [American flagfish](/species/american-flagfish) handles cooler water and serves a different aesthetic. ### Single-Species & Species-Only Setups The cleanest setup for *Aplocheilus lineatus* is a species-only tank with one male and two to three females in a 20-long. Males display, females hide in the floating plants, and feeding response is instantaneous. Add too many males in too small a tank and the dominant fish will harass the others into hiding spots until they stop eating. Keep the M:F ratio at 1:2 or 1:3. ## Breeding Golden Wonder Killifish Unlike annual killifish that need peat substrate and dry storage of eggs, *Aplocheilus lineatus* is a non-annual egg scatterer that breeds readily in a standard planted tank. This is the gateway killifish for hobbyists who want to learn species breeding without the dry-incubation complexity of *Nothobranchius*. ### Conditioning & Spawning Triggers Condition the breeding pair (or 1M:2F trio) on heavy live foods for 10-14 days - black worms, brine shrimp, mosquito larvae. Bump the temperature to 78-80°F and perform a 30% cool-water change to simulate monsoon-season inflow. Females in spawning condition develop visibly rounded bellies; the male intensifies in color and starts driving the female through the floating plant cover. ### Egg-Scattering Behavior & Mop Setup The female deposits eggs one or two at a time on yarn spawning mops, java moss, or the root mass of floating plants over a period of one to two weeks. Eggs are tough, pinhead-sized, and can be removed daily and incubated separately in a small jar with an airstone, or left in the parent tank with heavy plant cover for the fry to hide in. Eggs typically hatch in 12-14 days at 78°F. Faster at higher temps, slower at lower. ### Raising Fry Move fry to a separate grow-out tank as soon as they are free-swimming. They are surface feeders from day one and will not search the bottom for food. Start with microworms and vinegar eels for the first week, then transition to newly hatched baby brine shrimp once the fry can take them. Growth is fast - juveniles hit 1 inch in 6-8 weeks on a heavy live-food diet. ## Common Health Issues Golden Wonders are hardy, but two problems show up routinely. Both are tied more to husbandry than to the species itself. ### Ich & Skin Flukes Ich (*Ichthyophthirius multifiliis*) shows up as white grain-of-salt spots on the fins and body, typically after a temperature drop or a stressful move. Treat by raising the tank temperature to 86°F for 10-14 days, supplemented by aquarium salt at 1 tablespoon per 5 gallons or a standard ich medication if the fish are weakened. Surface fish stressed by ich will hang at odd angles or rest on plants - watch for posture changes before spots are visible. Skin and gill flukes (*Gyrodactylus*, *Dactylogyrus*) are common on imported wild stock. Symptoms include flashing against decor, clamped fins, and rapid gill movement. Praziquantel is the standard treatment; quarantine new arrivals for 2-3 weeks and dose during quarantine to avoid introducing flukes to an established tank. ### Fin Rot & Bacterial Infections Fin rot in Golden Wonders is almost always traceable to one of three causes: dirty water, aggression from another male killifish, or a netting injury that did not heal. Catch it early when fin edges look grayed or frayed; perform a 50% water change, raise water quality with daily 25% changes for a week, and treat with a broad-spectrum antibiotic if the rot has reached the fin base. Weekly partial water changes and a tight lid (preventing self-injury from jumping into glass) prevent most cases. ## Where to Buy & What to Look For Golden Wonders are widely available at independent fish stores and far less common at big-box chains. The species ships well as juveniles but takes a few days to color up after a long bag. ### Selecting Healthy Fish at Your Local Fish Store ### Spotting a Healthy Golden Wonder at Your LFS - [ ] Holding position just below the surface, not hiding on the bottom or wedged behind the filter - [ ] Vibrant gold body color with visible blue-green iridescence on the flanks - [ ] Belly full and rounded - not hollow or pinched (a sign of internal parasites or starvation) - [ ] Dorsal and anal fins held erect with no fraying, white edges, or red streaking - [ ] Clear, alert eyes with no cloudiness or popeye - [ ] Active hunting response when staff drops food on the surface - ask them to feed while you watch - [ ] Tank lid is tight and intact - tells you the store knows the species and has not lost stock to jumping - [ ] No floaters or dead fish in the same system, and no other tank in the row showing ich or fungus ### Online vs. LFS Sourcing Online vendors carry both the standard Golden Wonder and occasional rarer wild-type *Aplocheilus lineatus*. Shipping is hard on adults of this species - they bag-jump in transit and arrive stressed. Juveniles ship better and color up over the following month. A local fish store wins on every other axis. You see the fish hold a position near the surface (the single best behavioral health check), you watch it eat, you confirm the tank lid is sealed, and you start drip acclimation within an hour of purchase rather than 24-36 hours later. For a species whose number-one cause of death is jumping during stressed shipping, the LFS route is meaningfully safer. > **Buy Local** > > Always inspect Golden Wonder Killifish in person before buying. Watch for the surface-holding posture, full belly, and feeding response. Avoid stores where the killifish tank lid is propped open, where the fish are hanging at the bottom, or where neighboring tanks show disease - all three signal a system you do not want your new fish coming from. ### Acclimation Drip acclimate for 45-60 minutes. Water chemistry between stores can vary widely on this species (some stores keep them slightly brackish, others pure freshwater), and a fast plop-and-drop causes osmotic shock. Cover the acclimation bucket with a plate or a piece of plastic - they will jump out of an open bucket the same way they jump out of an aquarium. ## Quick Reference - **Tank size:** 20 gallons (long) minimum for 1M:2F; 29-40 gallons for groups - **Temperature:** 72-82°F - **pH:** 6.5-7.5 - **Hardness:** 5-20 dGH (tolerates slight brackish up to 1.005 SG) - **Diet:** Carnivore - floating pellets, frozen and live foods, especially insects and mosquito larvae - **Tankmates:** Corydoras, larger tetras, mollies, peaceful barbs - nothing that fits in a 4-inch fish's mouth - **Lid:** Tight-fitting, every gap sealed - non-negotiable - **Lifespan:** 3-5 years - **Difficulty:** Beginner to Intermediate For a deeper dive into hardy freshwater stocking options that mix well with surface-dwelling predators, see the [freshwater fish guide](/guides/freshwater-fish). ## Frequently Asked Questions ### How big do Golden Wonder Killifish get? Golden Wonder Killifish typically reach 3.5-4 inches in captivity. Males tend to be slightly larger and more colorful than females, displaying brighter gold and blue-green iridescence along their flanks. ### Are Golden Wonder Killifish aggressive? They are predatory toward smaller fish but generally peaceful with similarly sized or larger tank mates. Males can spar with each other, so keep one male per tank unless the aquarium is large enough to establish separate territories. ### What do Golden Wonder Killifish eat? They are carnivores that prefer surface foods - high-quality floating pellets, freeze-dried bloodworms, brine shrimp, and live insects like fruit flies. Live and frozen foods enhance coloration and encourage natural hunting behavior. ### Can Golden Wonder Killifish live with bettas? It is generally not recommended. Golden Wonders may nip fancy betta fins, and both species compete for surface territory. If attempted, use a large, heavily planted tank and monitor closely for aggression. ### Do Golden Wonder Killifish jump out of tanks? Yes - they are notorious jumpers. Always use a tight-fitting lid with no gaps. Even small openings around filter tubes or heater cords are escape routes this species will exploit. --- *Source: [FishStores.org](https://www.fishstores.org/species/golden-wonder-killifish)* *Last updated: April 24, 2026*