Foersch's killifish

Where they come from

Foersch's killifish (Nothobranchius foerschi) is one of those classic African annual killies. In the wild they come from seasonal pools that fill up in the rainy season and then dry out later. That whole lifestyle explains a lot: they grow fast, eat like little predators, and their eggs are built to wait out a dry spell.

Setting up their tank

You do not need a huge tank, but you do want it stable and easy to keep clean. A 10 gallon works nicely for a trio (1 male, 2 females) or a small group of juveniles growing out. They appreciate a calmer setup over a high-flow river tank.

• Tank size: 10 gallons for a trio, 20 long if you want a bigger group and less drama
• Filtration: sponge filter or gentle HOB with a prefilter sponge (they hate being blasted around)
• Temp: mid 70s F is a nice target; avoid cooking them in the 80s for long periods
• Lighting: moderate; too bright and they stay skittish unless you give lots of cover
• Cover: floating plants, moss, and clumps of stem plants break up sight lines

Substrate is where you choose your path. If you want to breed them the classic way, you will be using peat or coco fiber in a spawning container anyway, so the tank itself can be bare bottom or sand. I like bare bottom for adults because it makes it obvious if someone is off their food or if waste is building up.

Water-wise, they are usually pretty forgiving as long as it's clean and consistent. Neutral-ish water is fine, and slightly softer is often easier for breeding. What they do not tolerate is a dirty tank. These fish eat big foods and produce big waste for their size, so plan on water changes.

What to feed them

These are little carnivores. Mine always did best (color, growth, breeding) on a steady rotation of frozen and live foods. They will take pellets sometimes, but I treat pellets as backup, not the main plan.

• Frozen: bloodworms, brine shrimp, daphnia, mysis (chopped if needed)
• Live: blackworms (great but don't overdo it), mosquito larvae if you can source them safely, live brine shrimp for youngsters
• Dry: high-protein micro pellets or small granules, used sparingly

Feed smaller portions more often rather than one huge dump. Two small feedings a day keeps them growing without turning the tank into a soup.

How they behave and who they get along with

Males are bold and can be pushy, especially in smaller tanks or if the tank is too open. You will see flaring, chasing, and the occasional torn fin if you keep multiple males together without enough space and cover.

• Best grouping: 1 male with 2-3 females
• Multiple males: possible in a larger, heavily planted tank, but expect some sparring
• Tankmates: I usually skip them and keep a species tank

Could you do peaceful tankmates? Sometimes. But a lot of common community fish either outcompete them at feeding time or stress them out. And anything small enough can get investigated as food. If you want to keep it simple and actually see the killies acting natural, a species tank is the easy win.

Breeding tips

Breeding is half the fun with Nothobranchius. They are egg-buriers. The typical method is giving them a container of damp peat (or coco fiber) to spawn in, then you pull the medium, incubate the eggs out of water, and later re-wet to hatch.

• Spawning setup: a small plastic container or glass dish filled with boiled, rinsed peat or coco fiber
• How long to leave it: 3-7 days is a good rhythm, then swap for a fresh one
• Conditioning: heavy frozen/live foods for a week or two makes a big difference
• Incubation: store the squeezed-damp peat in a bag/container at room temp, dark place
• Hatching: re-wet with cooler water; adding a bit of infusoria-rich water can help first foods

Incubation time varies by strain and temperature, so do not panic if your timeline does not match someone else's forum post. I check a small sample of peat every couple weeks with a flashlight. If you see eyes in the eggs, you're getting close.

For raising fry, the first week is the hurdle. Freshly hatched brine shrimp is the workhorse food. Keep the grow-out water clean, do small water changes, and do not overfeed. They grow fast, and the runts get left behind if you do not separate by size.

Common problems to watch for

Most issues I have seen with foerschi come from three things: dirty water, rough handling, and too much aggression in a small tank. They are tough in some ways, but once something starts going wrong it can move quickly.

• Fin damage from chasing: add cover, remove extra males, or move the bully
• Bloat/constipation from rich foods: rotate foods, add daphnia, do smaller feedings
• Bacterial issues after fin tears: clean water fixes more than meds do; quarantine if needed
• Jumping: gaps in the lid, startled fish, or chasing can lead to carpet surfing
• Short lifespan surprises: annual killies can age fast; keep your line going with eggs

If you want the most success with these, think simple: stable warm-ish water, gentle filtration, lots of cover, and a steady rotation of meaty foods. Do that, and they will show you why people get hooked on Nothobranchius.