Sporting a palette to rival any rainbow, killifish are often naturally short-lived and temperamental. But those who embrace them rarely turn back…
If you want bright, the world of killifish offers a vivid palette without the limp credit card or the brain-ache of saltwater.
IT WORRIES me when relative novices say “I’m going to start keeping marines because the colours are so much brighter”. I imagine a lot of spending, and headaches, then nine months on they are selling their whole set-up complete with a surviving toadstool coral, algaecoated live rock and two clownfish.
Beyond the standard community tank, freshwater fish have more to offer than many appreciate. If you want the challenge then go marine and enjoy it. But if you want bright, the world of killifish offers vivid colour without the limp credit card or the brain-ache of saltwater.
Killifish and relatives inhabit all tropical continents, they have a winning formula in the wild and with eye-popping colours, modest size, cheerful character and generally affordable price tags, they also have a winning formula for aquariums.
So why isn’t your tank full of killis? And why isn’t there an abundance of them in shops?
Killifish are micropredators, eating small insects, larvae and crustaceans. Their diet should be protein and fat heavy. Once settled, the common varieties are easy-going at feeding time, although it can be a different story at first. During the first two days to a week it’s best to offer frozen foods, ideally those that stay in the water column – white mosquito larvae, Daphnia and brineshrimp.
Recently imported killies may need several days of live foods before offering frozen. If adult fish are not used to dried foods they may shun them forever, so introduce some as early as possible.
Killifish have either ‘terminal’ or ‘superior’ mouth types. They are poor at picking food up from the substrate so fast-sinking foods are often ignored. Unnoticed food will go to waste – even bloodworm may be overlooked when it’s lying still on the bottom of the aquarium. So, offer multiple small feeds a day rather than one larger meal.
A majority of killifish inhabit soft and acidic waters, often tannin stained and shaded by foliage.
Feeding raw beef heart will keep killifish strong and colourful. Use only good meat, not ‘tube’ bits, and blitz it in a blender
For a rough guide to a biotope we would be looking for a dark substrate, ideally soil based (low-nutrient shrimp soils work best) with a healthy amount of leaf litter (including bark chippings and coconut fibres) and not much else.
Wood can add structure to the tank but I’d lay it flat and build up substrate behind it for a more natural look. With a dark base, leaf litter and stained water, an electric-blue and scarlet-red fish really stands out.
The main challenge here is maintaining the carbonate hardness (KH), especially in a small tank. Soft water plus tannic and humic acids creates unstable conditions so I would aim for around 5°KH upwards – much lower and ph may fluctuate easily.
While softwater conditions are needed for breeding and egg development, many killifish are adaptable to harder water conditions. Experienced keepers often get great results keeping them in hard, alkaline tapwater set-ups, making for a more stable environment.
Killifish seem to enjoy clearwater planted tanks just as much as a leafy biotope set-up – just the kind of bright, clean, colourful aquarium that many aspiring marine keepers are looking for.
With killifish, you can buy ‘dry’ eggs, posted to you by sellers and enthusiasts from around the world. By evolving eggs which can be dried (and sometimes need to be), killifish have been able to inhabit temporary bodies of water – and we can use this to our advantage for ease of transport! Hatching the eggs needs only simple equipment, like air-driven sponge filters, and can be performed in plastic tubs rather than glass tanks. Killifish fry are ready to feed straight away, grow quickly, and soon move on to larger and larger foods.
Compatibility with others
Many killifish enthusiasts keep multiple small tanks with one species in each, usually with no other tank mates. I’ve kept them this way and enjoyed it – and it also helps to avoid hybridisation if you want to breed, but it’s not the only way to keep these lively, determined, fish.
Killifish are feisty, bright, feature fish and competition with other feature fish won’t end well. Mixed with dwarf cichlids the killifish will suffer; mixed with guppies the guppies will suffer.
Tank mates need to be almost nondescript and not too characterful, and also large enough to avoid the surprisingly wide mouth of a killifish. For all but the largest species, an adult Neon tetra is safe but young Neons may be snapped up by some larger adult killifish.
Annual & non-annual lifespan
Killifish can be split into two groups as far as lifespan is concerned – annual and non-annual.
West African Nothobranchius and most South American species, apart from Rivulus, are ‘annuals’, meaning they inhabit temporary water bodies that dry up annually and so the adults perish, leaving eggs behind them. They are so adapted to this shortened life that even when kept in an aquarium they die young when compared to most fish.
Temperature has a large influence on a killifish’s exact lifespan. In
With their vibrant colours, modest size, cheerful character and generally affordable price tags, killifish have a winning formula for the aquarium
warmer conditions, around 26°C, it may be just six months but keep them cool, around 22°C, and more than 12 months is achievable. ‘Non-annuals’ such as Aphyosemion,
Fundulopanchax and Rivulus reside in more permanent habitats mostly (but not exclusively and most species’ eggs can be ‘dried’). They have a longer life than the annuals with two or three years being the norm, again being temperature dependent.
These fish jump!
Be aware of the jumping ability of killifish! In the wild they have adjusted to living in extremely small habitats, sometimes just puddles where a batch of fry can generate high competition between themselves as they reach maturity.
Often, less dominant fish need to move to another body of water under their own power and the only way to do that is by hopping and jumping across forest floor. They will also jump out of the water to catch insects above the surface, which can result in them exiting a tank, and ending up on the floor. For this reason they require a close-fitting lid,
The words ‘aphyos’ and ‘semion’ translate from Greek into ‘small flag’ (or banner), referring to the lyretail fins of the males.
This is likely the best genus to keep if you are new to keeping killifish.
Aphyosemion species are adaptable to a range of water parameters. They are relatively robust, easy to breed, non-annual fish, full of the usual killifish charisma and the most suitable to mix with other tank mates. Most of these attributes are also shared with Fundulopanchax.
Habitat & distribution
Aphyosemion species come from western Africa. Hot spot areas include Gabon, Equatorial Guinea and Cameroon with many species coming from this group if countries. They are also found from Togo to Chad in the north, southern Democratic Republic of the Congo to the south and everywhere in between these countries.
They live in slow-moving, aged waters including lowland rainforest and coastal rainforest streams, swamps, pools and river basins. Mostly these habitats are soil bottomed, shaded by forest growth and contain lots of leaf litter, wood and seed pods. Some species live in savannah streams with soil and sandy substrates; an odd few species live at higher altitude in similar situations.
Killifish are feisty, bright, feature fish
below: A typical killifish habitat on the forest floor.
Above: Small, feisty, colourful and delicate.
Line-bred Golden australe males.
Natural strain chocolate Australe.