Freshwater Fish: Care Guides & Tank Setup

Freshwater fishkeeping is where most aquarists start — and where some of the most persistent misinformation lives, especially around 'easy' species sold with minimal care instructions. This section covers what popular freshwater fish actually need, beyond what's printed on the store packaging.

What This Section Covers

Freshwater fishkeeping spans an enormous range — from a single betta in a 5-gallon tank to large planted community tanks with dozens of species. Rather than generic "top 10 beginner fish" lists, our freshwater guides focus on what a specific species actually needs, including the gaps between store/packaging information and real-world requirements (tank size, heating, water parameters, and realistic tank mate options).

This section is actively expanding — we're working through our freshwater species library to bring every guide up to the same standard as our betta fish care guide: real tank size minimums, accurate water parameters, and an honest look at tank mate compatibility.

Species Guides

Popular Freshwater Fish

Vibrant red and blue veiltail betta fish flaring its fins in a planted aquarium
Freshwater Fish

Betta Fish Care Guide: Tank Size, Water Temperature & Tank Mates

Bettas are sold as 'low maintenance,' but a healthy betta needs more than a bowl. Here's what tank size, heating, and filtration actually look like in practice.

Betta Fish: Varieties & Health

Several betta fish of different fin types and colors in side-by-side aquarium displays
Freshwater Fish

Betta Fish Types, Fin Shapes, and Color Varieties Explained

Veiltail, halfmoon, crowntail, plakat, dragon scale, marble, koi — betta fish come in an enormous range of fin types and colors. Here's what the names mean and what actually changes about care.
A betta fish with a small patch of cottony fungal growth near its fin edge
Freshwater Fish

Betta Fish Fungal Infections: Symptoms, Causes & Treatment

Fungal infections in bettas show up as cottony white or grey tufts, usually following an injury or a stretch of poor water quality. Here's how to identify, treat, and prevent them.
Close-up of a betta fish showing a patch of skin discoloration along its side
Freshwater Fish

Why Is My Betta's Skin Peeling? Causes and What to Do

A betta with visibly peeling or sloughing skin needs prompt attention. Here's how to distinguish normal slime coat activity from chemical burns, columnaris, and parasitic infections.

Fish Skin Peeling: Causes Across Species

Close-up of a freshwater fish showing a patch of skin discoloration along its flank
Freshwater Fish

Why Is My Fish's Skin Peeling? Common Causes Across Species

Skin peeling shows up across many aquarium fish species, but the causes — and the urgency — vary widely. Here's how to tell what's normal, what's a water quality issue, and what needs treatment.
A freshwater angelfish with visible vertical stress bars swimming near plants
Freshwater Fish

Why Is My Angelfish's Skin Peeling? Causes and What to Check

Before treating 'skin peeling' on an angelfish, make sure it isn't stress bars — a normal, temporary color change. Here's how to tell the difference, and what real skin damage usually means.
A koi swimming near the surface of an outdoor pond, showing a patch of pale discoloration on its side
Freshwater Fish

Why Is My Koi's Skin Peeling? Ulcers, Parasites & Pond Factors

Koi skin peeling and ulcers are usually linked to bacterial infections, parasites, or seasonal pond changes — but a few possibilities, including a viral disease, need to be ruled out.
An Oscar fish showing small pits along its head and lateral line
Freshwater Fish

Why Is My Oscar Fish's Skin Peeling Off? Hole-in-the-Head & Other Causes

Pitting or skin erosion on an Oscar's head and lateral line is the hallmark of hole-in-the-head disease — linked to diet, water quality, and Hexamita. Here's how it develops and how to address it.
A goldfish swimming in a planted aquarium, showing a small pale patch on its side
Freshwater Fish

Why Is My Goldfish's Skin Peeling? Causes and What to Check First

Goldfish skin peeling is frequently linked to water quality — goldfish produce a lot of waste relative to their typical housing. Here's what to check first, and what else can be going on.

African Cichlid Tanks

Brightly colored Mbuna cichlids grazing on algae-covered rocks in a Lake Malawi-style aquarium
Freshwater Fish

Best Food for Mbuna Cichlids: Why Diet Matters More Than for Almost Any Other Fish

Mbuna cichlids are sold in the same aisle as every other 'cichlid pellet' — but feeding them like a generic cichlid is one of the most common causes of bloat, organ damage, and early death in this group.
Colorful male peacock cichlids (Aulonocara) swimming over a sand substrate in a 75-gallon aquarium
Freshwater Fish

75-Gallon Peacock Cichlid Tank: How Many Fish and What Setup Works

75 gallons is a popular and genuinely workable size for a peacock cichlid tank — but how you split that space between males, females, and other species makes or breaks the result.
Close-up of a cichlid with a cloudy, hazy film over one eye
Freshwater Fish

Cichlids With Cloudy Eyes: Causes, Treatment & When to Worry

Cloudy eyes in cichlids most often start as a water quality problem, not a disease — but injury, infection, and even diet can all produce the same visible symptom. Here's how to tell them apart.
A small container of Epsom salt next to an aquarium, used for treating constipation in African cichlids
Freshwater Fish

Epsom Salt for African Cichlids: When It Helps and How to Use It

Epsom salt is a widely used, low-risk supportive treatment for constipation and early bloat-like symptoms in African cichlids — but it's a supportive measure, not a cure, and dosing matters.
A piece of driftwood in an aquarium, with tannins visibly tinting the water a light brown
Freshwater Fish

Driftwood in a Cichlid Tank: Does It Work With African Cichlids?

Driftwood looks great and is a go-to for planted tanks, but it releases tannins that soften and acidify water — the opposite of the hard, alkaline conditions most African cichlids need.
A school of silver Bala sharks swimming in a large planted aquarium
Freshwater Fish

Bala Sharks With Cichlids: Why This Common Pairing Usually Doesn't Work

Bala sharks show up in a lot of 'cichlid tankmate' suggestion lists, but their adult size, schooling needs, and water chemistry preferences make them a difficult fit for most African cichlid setups.
A peacock eel (Macrognathus siamensis) partially buried in sand substrate
Freshwater Fish

Peacock Eel With Cichlids: Is This a Workable Combination?

Peacock eels are burrowing, soft-water fish — two traits that put them at odds with the rock-heavy, hard-alkaline-water setups most African cichlids need. Here's what actually matters for this pairing.

Livebearers & Community Fish

Brightly colored male guppies with flowing tails swimming in a planted aquarium
Freshwater Fish

Guppy Fish Care: Tank Size, Water Parameters & Breeding Basics

Guppies are sold as the ultimate easy beginner fish — and mostly, that reputation holds up. But a few realities (especially around breeding) catch new keepers off guard.
A double-tail (split-tail) guppy showing its divided caudal fin
Freshwater Fish

Split-Tail (Double Tail) Guppy: What It Is and Whether to Breed It

A guppy with a divided, 'split' tail fin isn't necessarily injured or deformed — it can be a deliberately bred genetic trait. But the genetics behind it come with real breeding caveats.
An emaciated guppy with faded coloration, a symptom sometimes associated with fish tuberculosis
Freshwater Fish

Guppy Tuberculosis (Fish TB): Symptoms, Treatment & Human Risk

Fish tuberculosis is a chronic, largely incurable bacterial disease — and one of the few aquarium fish diseases with a documented, if low, risk of transmission to humans through skin contact.
A male sailfin molly displaying its large dorsal sail fin in a planted aquarium
Freshwater Fish

Sailfin Molly Care Guide: Tank Size, Water Parameters & the Sailfin Display

Sailfin mollies are sold small but grow large, need harder and sometimes brackish water, and the male's namesake 'sail' is a display feature with its own care implications.
A solid black molly fish swimming in a planted freshwater aquarium
Freshwater Fish

Black Molly Care Guide: Tank Size, Water Parameters & Color Changes

Black mollies are hardy, easygoing livebearers — but their solid-black coloring is a selectively bred color morph, not a separate species, and it can shift with age, stress, or diet.
A sailfin molly and a shortfin molly swimming together in a community aquarium
Freshwater Fish

Can Sailfin Mollies Breed With Regular Mollies? What to Expect

Sailfin mollies (Poecilia latipinna) and common shortfin mollies are different species but closely related enough to interbreed — and in a mixed tank, they often will.
A male American flagfish displaying its red and blue-green coloration in a planted aquarium
Freshwater Fish

American Flagfish Care Guide: The Algae-Eater With a Temper

American flagfish are one of the few fish that reliably eat hair and beard algae — but their territorial temperament means they're not the drop-in-anywhere community fish their small size suggests.
A male American flagfish displaying territorial posturing toward another fish near aquarium plants
Freshwater Fish

Are American Flagfish Aggressive? What to Expect and How to Manage It

American flagfish are sold as easy community algae-eaters, but territorial and fin-nipping behavior is common enough that tank mate selection deserves real thought.

Catfish & Bottom Dwellers

A boldly spotted L-number pleco resting on driftwood, the pattern sometimes marketed as 'stingray pleco'
Freshwater Fish

Stingray Pleco Care: What This Trade Name Actually Means

'Stingray pleco' describes a pattern, not a species — a bold, spotted coloration found across several different L-number plecos. Here's what to know before buying one under this name.
A pleco resting near the substrate of an aquarium, with visible waste nearby
Freshwater Fish

Pleco Poop: What's Normal, What Colors Mean, and Bioload Basics

Plecos produce a lot of waste relative to their size — and that waste's appearance can be a surprisingly useful, low-effort signal of diet, digestion, and overall tank health.
A corydoras catfish with a visibly swollen abdomen resting on aquarium substrate
Freshwater Fish

Bloated Cory Catfish: Causes, Dropsy Warning Signs & Treatment

Most bloated corydoras cases are overfeeding or constipation and resolve with simple steps — but a swollen abdomen with raised scales is a different, more serious situation.
A channel catfish in shallow water, illustrating its size relative to typical aquarium fish
Freshwater Fish

Channel Catfish Tank Conditions: Why This Fish Doesn't Belong in Most Aquariums

Channel catfish are native North American game fish that can reach 2+ feet and tens of pounds — sizes that make 'tank conditions' almost the wrong question for a home aquarium.
A group of Colombian shark catfish swimming together in a large aquarium
Freshwater Fish

Colombian Shark Catfish Care Guide: Tank Size, Diet & the Brackish Question

Colombian shark catfish are sold as small, hardy community fish — but they grow to a foot or more, need to be kept in groups, and their natural habitat raises a long-term brackish water question.
A Berney's catfish, an Australian native shark catfish, swimming in a large aquarium
Freshwater Fish

Berney's Shark Catfish: Care Guide for This Australian Native Species

Berney's catfish is an Australian native relative of the Colombian shark catfish — sharing the same large-adult-size and freshwater-to-brackish considerations, but rarely seen outside native fish circles.
A small, flattened Asian stream catfish resting on sand substrate in an aquarium
Freshwater Fish

How to Care for 'Asian Banjo Catfish' (and What the Name Actually Means)

'Asian banjo catfish' is a common-name mismatch — true banjo catfish (Aspredinidae) are South American. Here's what's likely meant, and how to care for it.

Big Tank Centerpiece Fish

A Red Jardini arowana swimming near the surface of a large aquarium
Freshwater Fish

Red Jardini Arowana Care Guide: Tank Size, Diet & Long-Term Commitment

Red Jardini arowana are sold as striking juveniles a few inches long — but they grow into 2-foot predators that need a tank measured in hundreds of gallons, not a typical 'big' aquarium.
A thermometer reading inside a large arowana aquarium
Freshwater Fish

Arowana Water Temperature: Ideal Range and Why Stability Matters

The ideal temperature range for arowana isn't complicated — the real challenge is heating and maintaining stability across a tank measured in hundreds of gallons.
A group of discus fish swimming in a tall planted aquarium
Freshwater Fish

Is a 55-Gallon Tank Big Enough for Discus?

A standard 55-gallon tank can house a small group of discus, but its shape — long and not especially tall — is a bigger limiting factor than the gallon number suggests.
A freshwater aquarium stocked with several fish commonly given 'shark' common names
Freshwater Fish

What Are the Fish That Swim With Sharks? (And What If You Mean Aquarium 'Sharks'?)

Remoras and pilot fish swim with real sharks in the ocean — but most people searching this phrase in an aquarium context are really asking about freshwater fish marketed as 'sharks.'

Tetras, Nano Tanks & Common Health Questions

Small, colorful Endler's livebearers swimming in a heavily planted nano aquarium
Freshwater Fish

Can Endler's Livebearers Live in a 5-Gallon Tank?

Endler's livebearers are small enough to fit a 5-gallon tank on paper — but their prolific breeding and a small tank's thin bioload margin make this a setup that needs careful planning.
A neon tetra with faded color swimming away from its school, a sign sometimes mistaken for fungus
Freshwater Fish

'Neon Tetra Fungus': Is It Actually a Fungal Infection or Neon Tetra Disease?

'Fungus' on a neon tetra usually means one of two very different things — a treatable fungal infection, or neon tetra disease, which isn't a fungus and has no reliable cure.
A group of black skirt tetras swimming together in a planted aquarium
Freshwater Fish

Why Is My Black Skirt Tetra Being Aggressive? (And How to Fix It)

Black skirt tetra aggression — chasing, fin-nipping — is most often a group-size problem, not a fixed personality trait. Here's why, and what tends to fix it.
A colorful male dwarf gourami swimming among plants in a community aquarium
Freshwater Fish

Dwarf Gourami Care Guide: Tank Setup, Diet & the DGIV Health Risk

Dwarf gouramis are peaceful, colorful, and related to bettas — but a common viral disease in commercially-farmed stock makes careful sourcing and quarantine unusually important for this species.
A fancy goldfish with a rounded body shape swimming in a planted aquarium
Freshwater Fish

Why Do Some Goldfish Look Deformed? Breeding vs. Health Issues

Bubble eyes, rounded bodies, curled fins — many 'deformed' goldfish traits are intentional breeding results. But a sudden change in shape or posture is a different story.

Brackish & Specialty Freshwater Fish

A dragon goby partially buried in sand substrate with only its head visible
Freshwater Fish

Dragon Goby (Violet Goby) Care Guide: Tank Size, Substrate & Diet

Often sold in freshwater fish sections, the dragon goby (violet goby) is actually a brackish-water species with a long body, poor eyesight, and a habit of burrowing in soft sand. Here's what it really needs.
A dragon goby with only its head and dorsal fin visible above a sand substrate
Freshwater Fish

Do Dragon Gobies Bury Themselves? Normal Behavior vs. Warning Signs

If your dragon goby spends most of the day buried with just its head showing, that's normal — not a sign something's wrong. Here's why they do it, and what substrate makes it safe.
A dragon goby emerging from sand to take a sinking food pellet
Freshwater Fish

What Can I Feed My Dragon Goby? Diet, Picky Eaters & Feeding Tips

Dragon gobies sift sand for microscopic food in the wild, which is part of why they can seem reluctant to eat in aquariums. Here's how to feed them effectively, including what to do with new arrivals that won't eat.
A green spotted pufferfish with a yellow-green spotted back and white belly resting near plants
Freshwater Fish

Green Spotted Pufferfish Care Guide: Salinity, Diet & Tank Mates

Green spotted puffers are often sold in freshwater tanks as juveniles, but their salinity needs increase as they age, their teeth never stop growing, and most don't tolerate tank mates well. Here's the realistic picture.
A tall-bodied altum angelfish swimming among driftwood and leaf litter in a blackwater-style aquarium
Freshwater Fish

Altum Angelfish Care Guide: Tank Height, Soft Water & Group Size

Often confused with the common angelfish, Pterophyllum altum is taller-bodied, far more sensitive to water chemistry, and needs an unusually tall tank. Here's what sets altum care apart.
Close-up of white aragonite reef sand substrate in a freshwater aquarium with rockwork
Freshwater Fish

Can You Use Reef Sand in a Freshwater Tank? Hardness, pH & Best Uses

Reef sand isn't just decor — its calcium carbonate content slowly raises pH and hardness, which makes it a useful tool for some freshwater tanks and a poor fit for others.

Brackish Tanks, Paludariums & Surface-Dwelling Oddballs

Brackish aquarium with mangrove roots, sandy substrate, and fish near the water's surface
Freshwater Fish

Brackish Water Aquarium Fish: Setup, Salinity & Species Guide

Brackish water — the mix of fresh and salt found in estuaries and mangroves — is its own aquarium category, with its own salinity targets, equipment, and species list. Here's how to set one up properly.
Paludarium with a sloped sand bank, mangrove-style roots, and shallow brackish water housing fiddler crabs
Freshwater Fish

Brackish Water Paludarium: Setup Guide for Mangrove & Estuary-Style Tanks

A brackish paludarium recreates a slice of mangrove or estuary — land and water together, at low salinity — and it's one of the few setups where fiddler crabs, mudskippers, and brackish fish can realistically share a tank.
Four-eyed fish swimming at the water's surface with its distinctive split, protruding eyes visible above the waterline
Freshwater Fish

Four-Eyed Fish (Anableps anableps) Care Guide: Tank Setup, Salinity & Split-Pupil Eyes

The four-eyed fish doesn't have four eyes — it has two eyes, each split into upper and lower halves, letting it watch for danger in the air and food in the water at the same time. That split vision shapes nearly everything about how it's kept.
African butterfly fish with broad wing-like pectoral fins resting near the water's surface among floating plants
Freshwater Fish

African Butterfly Fish (Pantodon buchholzi) Care Guide: Tank Size, Diet & Jumping

With broad, wing-like pectoral fins and a flattened, upturned mouth built for ambushing insects at the surface, the African butterfly fish is one of the more distinctive freshwater 'oddballs' — and one of the most prone to jumping out of an open tank.
Amazon leaffish camouflaged among dead leaf litter, body shape and coloration closely resembling a fallen leaf
Freshwater Fish

Amazon Leaffish (Monocirrhus polyacanthus) Care Guide: Camouflage, Diet & Tank Setup

Shaped, colored, and even angled to look exactly like a dead leaf drifting in slow water, the Amazon leaffish is one of the most extreme camouflage specialists in the freshwater hobby — and one of the most demanding to feed.

Breeding & Fry Care

A cluster of small translucent fish eggs attached to an aquarium plant leaf
Freshwater Fish

How Long Does It Take for Fish Eggs to Hatch? A Species-by-Species Look

Most aquarium fish eggs hatch within 1-7 days, with temperature as the biggest variable — but livebearers skip eggs entirely, and a few species can take weeks or months.
A guppy with several free-swimming fry in a planted aquarium
Freshwater Fish

The Easiest Freshwater Fish to Breed at Home

Livebearers like guppies and mollies are the easiest freshwater fish to breed by a wide margin — no egg stage, no special triggers, and fry that are born ready to eat. Here's how other species compare.
A panda corydoras catfish resting near the substrate in a planted aquarium
Freshwater Fish

Panda Corydoras Breeding: The Cool Water Change Trigger Explained

Panda corydoras breeding has a genuinely reliable trigger — a cool water change mimicking a rain event — which makes it one of the more achievable breeding projects for egg-scattering catfish.
A pair of brightly colored rainbowfish swimming near fine-leaved aquarium plants
Freshwater Fish

Rainbowfish Fry: Breeding, Egg Collection, and Raising the Young

Rainbowfish are among the more approachable egg-scatterers to breed — they spawn a few eggs daily over several weeks, but success depends on daily egg collection and getting fry food right from day one.
A small group of otocinclus catfish grazing on algae-covered glass in a planted aquarium
Freshwater Fish

Otocinclus Fry: Why Breeding Them Is So Rare (and What to Do If It Happens)

Otocinclus breeding in home aquariums is rare enough that most of the supply is still wild-caught — here's why, what successful spawns look like, and how fry are raised when it does happen.

Cichlid Species Guides

A large red and orange cichlid with dark vertical barring swimming in an aquarium
Freshwater Fish

Red Tiger Motaguense Cichlid: What This Hybrid Actually Is

Red Tiger Motaguense isn't a single species — it's a hybrid trade name for selectively bred Central American cichlids, and that hybrid origin explains both the striking coloration and the variability between individuals.
A small yellowish cichlid with faint dark markings resting near rocks in a freshwater aquarium
Freshwater Fish

Amatitlania nanolutea Care Guide: A Dwarf Central American Cichlid

Amatitlania nanolutea is a dwarf relative of the convict cichlid — small enough for a 20-gallon tank, with the same substrate-spawning, biparental breeding behavior as its better-known cousin.
A medium-sized Central American cichlid with greenish-grey coloration swimming over gravel substrate
Freshwater Fish

Astatheros robertsoni Care Guide: Tank Size, Diet & Temperament

Astatheros robertsoni is a medium-sized river cichlid from Chiapas — large enough to need real space, but considerably more manageable than the biggest Central American cichlids.
A male African cichlid with a bright orange patch along its back swimming over rocky substrate
Freshwater Fish

Kyoga Flameback Cichlid: Care Guide for This Lake Victoria Basin Species

The Kyoga Flameback is a haplochromine cichlid from Lake Kyoga in Uganda's Lake Victoria basin — closely related in care needs to Lake Malawi mbuna, but generally smaller and less relentlessly aggressive.
A pale white and gold cichlid with a rounded body swimming in a planted aquarium
Freshwater Fish

White Severum Fish: Care Guide for This Peaceful Color Morph

The white severum is a color morph of Heros severus, the South American severum cichlid — a large but unusually peaceful cichlid often kept alongside discus.

Freshwater Species Spotlights & Health

A gold-bodied cichlid with a distinct red-orange patch on its head and forehead swimming in a planted aquarium
Freshwater Fish

Red-Headed Severum: Care Guide for This Color Morph

The red-headed severum is a color morph of Heros severus with a gold or green body and a striking red-orange patch on the head — care needs are the same as other severum morphs, including the white severum.
A dark-bodied cichlid with iridescent blue-green speckling swimming in a rocky aquarium
Freshwater Fish

How Fast Do Jack Dempseys Grow? A Realistic Size Timeline

Jack Dempseys can grow several inches in their first year alone — but how close they get to their full 8-10+ inch adult size depends heavily on tank size, feeding, and water quality.
A collage-style aquarium scene with several brightly colored and unusually patterned freshwater fish
Freshwater Fish

The Coolest Freshwater Aquarium Fish (Beyond the Usual Top-10 Lists)

From a hybrid cichlid with no fixed species identity to a killifish whose eggs can pause development for months, these freshwater fish stand out for reasons beyond just color.
A close-up of an aquarium fish showing small white spots on its fins and body, a common sign of a parasitic infection
Freshwater Fish

Combating Parasites in Aquarium Fish: Recognition, Prevention, and Treatment

Ich, velvet, flukes, and internal worms are among the most common parasites affecting aquarium fish — recognizable by a handful of visual and behavioral signs, and largely preventable through quarantine.
A small, vividly blue killifish with pearl-like spots swimming over a dark peat substrate
Freshwater Fish

Argentine Pearl Fish: The Annual Killifish With Dormant Eggs

The Argentine pearl fish is an annual killifish whose eggs can survive in damp peat for weeks to months via diapause — a breeding strategy tied to its native temporary-pool habitat in Argentina.

Frequently Asked Questions

What's the best freshwater fish for a first tank?

It depends on tank size and goals, but fish that are frequently recommended for genuinely beginner-friendly setups include bettas (in a properly heated, filtered 5+ gallon tank — see our betta care guide), certain peaceful schooling tetras, and corydoras catfish. The common thread among good beginner choices is tolerance for a range of parameters and availability of clear, accurate care information — which, unfortunately, doesn't always match what's printed on store packaging.

Why do so many freshwater 'beginner fish' end up dying within weeks?

In most cases, it's not the fish — it's an uncycled tank (no established beneficial bacteria to process ammonia) combined with care information that understates real requirements (tank size, heating, filtration). Fish marketed as 'low maintenance,' like bettas in cups or goldfish in bowls, are often the most misrepresented in terms of actual long-term needs.