Best Breeding Colony Tanks in 2026 for Guppies and Endlers

Choosing the right tank for breeding guppies and endlers is less about finding a specialized “breeding tank” and more about understanding what these fish need to reproduce successfully at scale. Livebearers breed in anything — a jar, a bucket, a neglected 5-gallon. The question is what gives you the best combination of colony health, fry survival, and manageable maintenance.

The answer, for most breeders, is boring: standard glass tanks in 10 or 20-gallon sizes. They are cheap, stackable, widely available, and fit all standard equipment. The breeding magic happens in your management approach, not the tank itself.

Quick Picks

Need	Our Pick
Best overall breeding tank	Aqueon 10-Gallon Standard
Best colony tank	Aqueon 20-Gallon Long
Best display breeder	Ultum Nature Systems 5N Rimless
Best fry separator	Marina Hang-On Breeding Box

Tank Size Strategy

Single-Strain Breeding: 10 Gallons

A 10-gallon tank is the workhorse of guppy and endler breeding. It comfortably holds a breeding group of 2-3 males and 5-6 females with room for the first few batches of fry to grow. Once fry reach 2-3 weeks old, move them to a separate grow-out tank.

Setup per 10-gallon breeder:

• Sponge filter (shrimp-safe, gentle flow)
• Heater at 78degF
• Floating plants (guppy grass, water sprite, java moss)
• No substrate or fine sand (easier to spot and collect fry)
• Basic LED light on 8-hour timer

Colony Breeding: 20-Gallon Long

If you want a self-sustaining colony where adults and fry coexist with minimal intervention, the 20-gallon long is ideal. The extended footprint (30 inches) provides enough space for adults to swim actively and fry to find cover among floating plants.

In a heavily planted 20-gallon long, enough fry survive predation from adults to maintain and grow the colony without manual fry separation. This is the “set and observe” approach — feed, maintain water quality, and let the colony manage itself.

Display Breeding: 5-Gallon Rimless

For hobbyists who want to watch the breeding process in a beautiful setup — a single trio in a rimless nano tank makes a stunning desk display.

The 5-gallon size is adequate for a single male and two females, but fry must be removed within 1-2 weeks or the adults will eat them. This is a display and observation tank, not a production setup.

Separating Fry

In-Tank Solutions

Hang-on breeding boxes isolate pregnant females or trap fry in a separate compartment within the main tank. They use main tank water (so temperature and chemistry match) and require no additional equipment.

The limitation is stress. Confining a pregnant female in a small plastic box for days is stressful and can cause premature delivery or health issues. Use breeding boxes for no more than 24-48 hours — just long enough for the female to drop her fry, then release her back to the main tank.

Dedicated Grow-Out Tanks

The better approach is a separate grow-out tank. Move fry at 1-3 days old (or move pregnant females to a separate tank and return her after delivery). A simple 10-gallon with a sponge filter and floating plants gives fry space to grow without adult predation pressure.

Colony Management for Strain Maintenance

Guppy Colonies

For strain maintenance, keep single-strain colonies isolated. One male from a different strain that accidentally enters a colony can introduce unwanted genetics that take 3-4 generations to breed out.

Colony ratio: 1 male per 2-3 females. More females than males reduces harassment and gives each female recovery time between pregnancies.

Culling schedule: Grade males at 8-12 weeks when color and finnage are fully expressed. Keep the top 20-30% as breeders. Sell or cull the rest. For females, cull any showing weak color or body deformities.

Endler Colonies

Pure N-class endlers are increasingly rare and valuable. If maintaining N-class purity:

• Never house with guppies or hybrids
• Track lineage if possible
• Buy from verified N-class breeders
• Males are easy to identify by strain-specific patterns; females are harder to distinguish from hybrids

Endlers breed faster than guppies (shorter gestation, earlier maturity) and produce smaller broods (5-15 fry vs. 20-50+ for guppies). Colony growth is steady but less explosive.

Water Conditions for Maximum Breeding

Livebearers breed in a wide range of conditions, but optimal parameters maximize output:

• Temperature: 78-80degF (higher = faster metabolism = faster breeding cycle)
• pH: 7.0-7.8
• GH: 8-14 dGH (livebearers prefer moderately hard water)
• KH: 4-8 dKH
• Ammonia/Nitrite: 0 ppm (non-negotiable)
• Nitrate: Below 20 ppm

Higher temperatures shorten gestation periods (from 30 days at 76degF to 25 days at 82degF) but also shorten overall lifespan. Most breeders run at 78degF as a balance between breeding speed and fish longevity.

Multi-Tank Rack Setup

For serious breeding, a rack system with multiple tanks is the most space-efficient approach:

Typical rack layout (one 36-inch wire shelf unit):

• Shelf 1: Breeding colony #1 (10-gallon)
• Shelf 2: Breeding colony #2 (10-gallon)
• Shelf 3: Male grow-out (10-gallon)
• Shelf 4: Female grow-out (10-gallon)
• Shelf 5: Fry tank / Holding for sale (10-gallon)

This 5-tank setup lets you maintain 2 strains simultaneously with dedicated grow-out and sales holding. Expand by adding a second rack for more strains.

Frequently Asked Questions

How many guppies can I breed in a 10-gallon tank?

A breeding group of 2 males and 5-6 females is comfortable. With fry present (before moving to grow-out), total population can temporarily reach 30-40 before density becomes a problem.

Do I need separate tanks for males and females?

For selective breeding, yes — separate males and females once sexable (3-4 weeks) to control which fish breed. For colony breeding where you are selecting from the best offspring regardless, co-housing is fine.

How often do guppies breed?

Females drop fry every 25-30 days. A single female stores sperm and can produce multiple batches from a single mating. Even females purchased alone may already be pregnant from pet store exposure.

Is bare bottom or substrate better for breeding tanks?

Bare bottom is easier for maintenance — you can see and remove uneaten food, spot fry easily, and vacuum waste without navigating substrate. Substrate is better for colony tanks where aesthetics and biological stability matter more than fry visibility.

Can I breed guppies and endlers in the same tank?

You can, but they will hybridize freely. If maintaining strain purity is your goal, never house guppies and endlers together. If you want interesting hybrid variations and are not concerned about purity, mixed colonies produce diverse and often beautiful offspring.