Killifish / Aphanius mento – How I Hatch & Breed Them
Today I’m talking about Aphanius mento — and this will be fairly quick, mainly because by the time you receive the eggs… they’ve often already started hatching.
That’s just the nature of this species.
Why They Hatch So Fast
Unlike most annual killifish, Aphanius mento has a very short incubation period:
- Typically 7–15 days
- In my experience, usually closer to 7 days
So think about it:
The fish lays the eggs →
You collect them →
You confirm they’re viable →
They go in the post →
By the time they arrive, they’re wriggling.
This is one of the reasons you don’t see this species for sale very often. They hatch so quickly that shipping becomes a real problem — especially internationally. Many won’t survive long transit times.
Using breathable bags can buy you a little extra time, but it’s still risky.
The Good News – Yolk Sac Fry
One major advantage of Aphanius mento is that the fry hatch with a yolk sac.
That means:
- No feeding required for the first couple of days
- You’ve got breathing space
Once the yolk sac is absorbed, they’ll take baby brine shrimp almost immediately.
Water Conditions – This Is Important
This is a cool water species.
They can tolerate:
- Temperatures as low as 10°C
- Very comfortably around 18–21°C
Yes, they can survive warmer water — but it reduces lifespan dramatically.
Although sometimes labelled semi-annual, I prefer not to box them in. They typically live about 18 months, but I’ve personally had them reach three years by keeping them cooler.
If you keep them heated year-round, expect a shorter life.
Water Chemistry
This species does not like soft water.
Keep the water:
- Slightly hard
- Slightly alkaline
I buffer mine using shell substrate or crushed cockle shells.
If you keep them in soft water, they simply don’t thrive — and often die quickly.
Breeding Season & Spawning
They are seasonal breeders.
Expect eggs:
- April, May, June
- Occasionally slightly beyond that, but rarely
After a couple of months of heavy breeding, females become spent.
Aggression Warning
This species is extremely aggressive.
Males are highly territorial and will:
- Harass females constantly
- Kill rival males
Best setup:
- 1 male to at least 3 females
- Or, in larger setups, 2–3 males with 6–9 females (but expect a dominant male)
Oddly enough, when multiple males are present, the dominant male often focuses on rival males — which can take pressure off the females.
But make no mistake — they will fight, even in large tanks.
Tank Setup for Breeding
During breeding season:
- Remove dense plants
- Replace with wool spawning mops
They tend to lay eggs toward the bottom of the mop — they’re effectively bottom spawners.
Plants make egg collection difficult, and in small tanks males will hunt down fry.
Keep things simple and easy to manage.
Raising the Fry
Once the yolk sac is absorbed:
- Start with baby brine shrimp
- Add micro worms after a few days
- Move onto Grindal worms as they grow
They’ll take flake and frozen food eventually, but if you want them in prime breeding condition — use live food.
Growth & Appearance
They’re slow growers.
Males:
- 3–4 cm
- Turn an incredible electric blue in breeding condition
- Roughly twice the size of females
Females:
- Muddy green
- Smaller and more subtle
When males colour up, they’re absolutely stunning.
Genetic Weakness – A Real Issue
One thing I’ve noticed — and other breeders will agree — is that this species can crash genetically if you keep breeding from the same line.
Symptoms:
- Females stop laying
- Males become infertile
- Entire line dies out within 2–3 years
If possible, introduce fresh blood from wild-derived lines (F1 stock ideally). The available gene pool in the hobby isn’t always strong.
Final Thoughts on Aphanius mento
- Cool water species
- Hard, alkaline water preferred
- Fast hatching eggs (often hatch in transit)
- Highly aggressive
- Seasonal breeder
- Stunning males in condition
If you can get hold of them, they’re absolutely worth keeping. The males in breeding colour are electric, bold, and full of personality.
Just be ready for the aggression — and don’t rely on the post being gentle with the eggs.
