ARK - Arizona Rivulin Keepers


The purpose of this guide is to help new killifish hobbyists handle some of the peculiar conditions that can occur in the Phoenix metropolitan area in particular, but also throughout much of Arizona. The suggestions are based upon the experiences of other killifish keepers and we offer these to help you succeed with this colorful group of fish.

Keeping Killies in Arizona

by Allan Semeit

CHAPTER 1 - It's The Water

One of the keys to successfully keeping and breeding aquarium fishes is providing quality water conditions. While most aquarium fishes will adapt to your local water and live quite well, others may require some adjustments. Still others may require major changes before they will thrive and/or breed. In many cases, this means attempting to reproduce the natural water characteristics from where the fish originates. Let us examine some of the important water quality factors to see how they affect killifish.


Water hardness is used to describe the mineral content of your water. If water is considered to be hard, that means it has a relatively high mineral content of elements such as calcium and magnesium. Soft water is relatively free of these minerals. In the United States we usually measure total hardness in terms of Parts Per Million or ppm. Europeans use a different measure called a Degree of (German) Hardness or DH or GH. One degree of DH equals 17 ppm. There is no uniformly accepted standard so you will find both measurements used. Below is a rough division of hardness:

Parts Per Million:
ppm 0-50 - very soft
51-100 - moderately soft
101-150 - moderately hard
151-300 - hard
above 301 - very hard

Phoenix area water is very hard. It measures somewhere around 350-400 ppm of Total Hardness. This varies somewhat throughout the year, as well as from community to community. Knowing your approximate hardness can be important to successfully keeping killifish.

Since many of the popular killies originate in tropical rainforests with very soft water, many killie hobbyists try to replicate those water conditions. Most killie-keepers would say that a hardness of 50-150 ppm is about right for rainforest killies. Considering that our local water is three or four or more times harder, it is perhaps surprising that many of the rainforest species will thrive and breed in our tap water. You will find that most do just fine in Phoenix water. In fact, there are actually some advantages to maintaining rainforest killies in hard water. Colonel Joergen Scheel, one of the patron saints of killie-keeping, advocated using harder water. One of the reasons was that the pathogens (diseases, etc.) that affect soft water killies generally do not thrive in hard water. Another is that harder water is more stable (buffered) and is less likely to suddenly become hyper-acidic.

While most killies will adapt to Phoenix water conditions, you may encounter a few species of rainforest killifish, especially those that are wild imports, or those bred and raised in very soft water conditions, that do not prosper in regular Phoenix water conditions. Many South American annuals appear to belong to this category too. There are several ways to handle this:

1. You can add a peat (black-water) extract to the aquarium water. Peat is a natural material that tends to soften water and add beneficial organic compounds to it.

2a. You can gradually reduce the hardness by mixing in distilled or reverse osmosis (RO) water. Do not use pure distilled or reverse osmosis water. Your fish require some minerals in their water. That is why you blend in these with your tap water. Always be sure to SLOWLY adapt your fish to softer water. A rapid change in osmotic pressure can burst the gills and kill your fish.

2b. As a rule, do not use "softened" water. Water that goes through a water softener has the calcium and magnesium ions replaced with sodium ions. While this does lower the Total Hardness, often dramatically, the resulting water has an extremely high sodium content that can be detrimental to some fishes, their egg development and the growth of plants. Allan Semeit reported that "softened" water coming out of his kitchen tap measured 523-5 Total Dissolved Solids (TDS - see below) and 1 DH (17 ppm) compared to 492-3 TDS and 22 DH (374 ppm) from the unsoftened water from his front outside faucet.

3. Finally, if a species does poorly for you, despite providing "ideal conditions" trade them. You might have an incompatible pair. You might have any number of things that are affecting them. Let someone else have the opportunity to keep and breed them. Also let the new owner know what you have attempted.

Before you make any adjustments to your water, you need to know the quality of your water. One of the easiest ways is to contact your local water department. Most publish annual reports. Some are also available on-line. These are fairly general and can cover a large geographical area.

Another option is to purchase test kits and meters. Pool supply stores, hardware stores (such as HomeDepot) as well as aquarium stores sell kits to measure your hardness. Chemical reagents have a definite shelf-life, but these will tell you approximately what your water is like. Even more accurate than the kits are the electronic meters. There are several types of these. The first measures hardness only. Another one that is more commonly used by hobbyists is a meter that measures Total Dissolved Solids (TDS). TDS includes more than just the calcium/magnesium/sodium ions that we call "hardness." These extra elements can include other minerals and organics.

In summary, most rainforest killifish will adapt to Phoenix water without any need to soften it. These include favorites such as Fundulopanchax gardneri, Aphyosemion australe, and Epiplatys dageti. And don't forget that there are other killies besides those from the rainforests! Many of these, including the Lebias (formerly Aphanius) group, as well as most North American killies, actually prefer our unsoftened tap water.


Arizona water companies frequently use chloramine to kill bacteria. This persistent form of chlorine also will kill your fish. There are several methods of neutralizing or removing chloramine. The old technique of letting water "age" in a bucket or tub, maybe with an airstone added, does not work with chloramine, as it can remain potent in the water for a month or more.

The easiest method to remove chloramine from your tap water is to add a liquid neutralizer such as Kordon's Amquel. Add the recommended amount and the chloramine is eliminated. As a variation on this, Peter Unmack recommends using sodium thiosulphate - 111 g in a total of 200 ml solution - one or two drops per gallon. Peter notes it is an inexpensive alternative and that you can obtain sodium thiosulfate through photographic developer supply places.

A second option is to pre-filter your water before it goes into a reservoir with activated carbon or ammonia-removing crystals (for example: White Diamond Ammonia-Neutralizing Crystals from Marineland or Ammo-Chips from Aquarium Pharmaceuticals). Perhaps the ideal system has been described by Wright Huntley from the Bay Area Killifish Association. Wright runs his water through two carbon blocks. He rigorously tests the water leaving the first carbon block with a chlorine test kit. When the chloramine eventually punches through the first filter, he replaces it. The second filter prevents the small amount that got through the first filter from reaching his reservoir. He turns off the incoming water, discards the first carbon block, moves the second carbon block to where the first was, and then installs a new carbon block in the second filter, before turning the water back on.

A third option is to set up a reservoir and filter the water while it is in the reservoir. Allan Semeit has adopted this method and uses a large plastic storage tub that holds about 20 gallons. There is a submersible filter causing the water to move continuously. The filter contains a mix of activated carbon and ammonia-removing crystals. There is also a bag of these materials in the water. Additionally, there are strips of Poly-Filter (an absorbent filter material) in the tub. All of these materials are periodically replaced with fresh ones. Besides removing chloramine, these materials absorb harmful organics, toxic ammonia, heavy metals, phosphates, and help purify the water before use.

What system should you use? That will depend upon what tank or tanks you have, and how much water you change. As a rule of thumb, most fish, not just killifish, will benefit from a 10-20% water change (replacement) every week. Frequent small changes are better than massive ones.

Finally, whichever method you use, you should still "age" water for 24 hours before adding it to an established aquarium . "Aging" allows the water to warm to room temperature and lets any excess gases (such as carbon dioxide) to be released before the water goes into your tank. If you have ever noticed tiny bubbles on the sides of your aquarium after a water change, those are from excess gases being released from your water.


Living in the desert where summer daytime temperatures can exceed 110 degrees Fahrenheit can pose a real challenge to keeping killifish. Typical rainforest killies live in waters that are fairly constant year-round in temperature. For most of these, that temperature is about 72 degrees F. The killies found at higher elevations live in even cooler waters. How then does the hobbyist keep his killies at these temperatures?

Simply, here in Arizona, it isn't going to happen. At least, not at those temperatures - unless you want to pay for excessive air-conditioning during the summer and heating during the winter. However, you can still keep just about all killies in Arizona if they are maintained at typical room temperatures. For example, most people keep their house about 80-82 degrees during the summer and between 68-72 degrees during the winter. Killifish will generally do just fine at these ambient temperatures and ARK members report keeping a large number of rainforest killies without any difficulties at these temperatures.

With the gradual change from cool winter temperatures to our warmer summer temperatures, your killifish will tend to become more active. This applies even to those killifishes that have habitats that usually remain about 70-72 degrees. Contrary to what you might expect, many killies of these naturally cool-water killies breed more actively during the summer. Then when the temperatures drop closer to their natural range during the winter, these killies actually slow down and even stop breeding.

You may reside, or keep your fish, in a location that is not well insulated. Even if your temperatures range above and below those mentioned, you can still keep killies. There are a number of killies that tolerate, and even enjoy, higher temperatures. Pupfish, the desert fishes from the Middle East, Aplocheilus species, some Nothobranchius, and even some South American annuals prefer water in the 80s, and some can even tolerate it even warmer. Many of these same species can also tolerate cooler winter temperatures. You may have fewer choices in these circumstances, but you can still find killies that you can keep.

One caution about temperatures - AVOID locating your fish where they might experience rapid temperature changes. Do not place a tank in a window, or where the air conditioner/heater blows upon them. Sudden changes can weaken your fish and cause you to lose them. Gradual changes to the water are almost always recommended.

CHAPTER 2 - Housing Your Killies


There are many ways to keep killifish. Because of their great variation in habitats, not all killies can be handled in the same way. A killifish from a marine lagoon will have different requirements than one from a mountain stream. While most killies average about two inches in length, a few can reach six inches or larger, and some barely exceed an inch. Rather than attempt to cover all of the possibilities, we will focus on the "typical" killifish. The "typical" killifish would primarily include genera such as Aphyosemion, Epiplatys, and Fundulopanchax primarily from west Africa, Aplocheilus from India and southeast Asia, and Rivulus from central and South America.

The Display Approach Many hobbyists like to maintain display tanks. In general, killifish do not thrive in this environment. Most killies tend to be shy and timid when kept with more boisterous or active tankmates. If you want a large display tank, say a 26-gallon aquarium, you would probably have better success keeping a group of the same species of killie. Fundulopanchax gardneri, particularly the N'Sukka population, would be one good candidate for such a set-up. These are brightly colored and less shy than most killies. Both males and females of this population can be housed together.

Another display option, besides the single species aquarium, is a male-only approach. The absence of females tends to reduce possible male-to-male aggression. Some male killies seem to have a "rooster" mentality of killing every potential rival - and the lack of females tends to mute this. This males-only tank can be single species or contain a number of different killies. Be sure to provide plenty of hiding places! Since most female killifish can be difficult or impossible to distinguish by species, don't mix females unless you are very certain that you can tell them apart.

This leads to another option. You can consider maintaining two very different looking killies (both males and females). The two species should be of similar size and temperament. For example, you can successfully keep Epiplatys dageti and Aphyosemion australe together in a ten-gallon or larger aquarium. Both species tend to be peaceful and ignore each other. Allan Semeit reports keeping these two species for several years without problems. He noted that each species lays eggs that are distinctly different in size so you can tell which is spawning. He also incubated the eggs of both species together and raised the fry together as well.

The "Typical" Killifish Set-Up
The small size of killies allows you to maintain them in smaller tanks. Perhaps the most popular size of killifish aquarium is about two-gallons. This is usually either a two-gallon glass tank or a "medium" plastic Critter Keeper. Generally, you can permanently keep 2-4 adults in tanks of this size. The two-gallon tank is large enough that you can install a small filter (such as a sponge filter) and the volume of water is sufficient to reduce the chance of a rapid change of quality or temperature. Because of the relatively small tank size, killie hobbyists can house a large number of species in separate tanks in a minimal amount of space. The drawback to two-gallon tanks is their cost. A glass two-gallon tank or a plastic two-gallon (medium) plastic Critter Keeper will run about the same price as a ten-gallon aquarium.

As an alternative to two-gallon tanks, some hobbyists prefer to use ten-gallon tanks. When they need two-gallon set-ups, they make, or obtain, glass partitions that they silicon-cement into the ten-gallon tank. In this way they divide the tank into two or three compartments. These compartments also need to be well covered as most killies are excellent jumpers. The advantages to using ten-gallon tanks include price and uniformity.

The Hodgepodge
One of the afflictions associated with killie-keeping is having too many fish. To resolve this problem, killie-keepers use a variety of expedient containers. The development of plastic shoeboxes, shirtboxes, and the larger sizes has been a blessing. These containers, with their tight-fitting lids, are excellent for killies. The larger sizes with their wider surface area are wonderful "grow-out" tanks for maturing fry. The only draw-back to these types of plastic containers is their reduced visibility. This type of plastic is harder to see through than with a glass container or the plastic used in Critter Keepers.

Besides plastic shoe-boxes and sweater boxes, there are a variety of plastic boxes, jars, or whatever, that can be adapted to house killies. You might be surprised to discover suitable containers. Consider things like the larger pretzel and candy jars. If you have a deli nearby, check to see if they use glass pickle jars. They will usually be glad to have you take them off their hands. Many of these will hold about two gallons of water and can be recycled into fish tanks after their initial usage.

Whether you decide to keep killies only for display, or if you decide to breed them, you will find lots of options in housing these beauties. Again, be sure to have a tight-fitting cover.


Understanding several terms will help us with a discussion of filters. There are three general ways filters remove substances from aquarium water. These are:
  • Mechanical filtration is the collection of debris and other solids from the water.
  • Biological filtration uses helpful bacteria to convert toxic fish wastes to less harmful compounds.
  • Chemical filtration absorbs harmful products from the water and may also release beneficial substances into the water.

    When you set up your killies, what is the best type of filter to use? This answer can really vary. If you have set up a 10-gallon or larger tank, you have quite a few options. If you are asking about a two-gallon, or smaller, tank, your choices are more limited. Let's consider some options.

    Power outside (hanging) filters: Generally you want to avoid these. Although they can be excellent mechanical filters, they also provide an exit point where your fish can jump out of the tank. Killies are notorious jumpers. These filters are only suitable for 10-gallon or larger tanks.

    Power submersible filters: These can be very suitable for a killie tank and they serve primarily to remove debris from the water. Be sure to restrict the flow to a gentle, slow movement. As a general rule, killies do not like a strong water flow. In fact, if you are having a problem with some, particularly Nothobranchius species, try to really restrict the water circulation to a minimum. Power submersible filters are most suitable for 10-gallon or larger tanks.

    Undergravel filters: These can be very adaptable and are excellent for "permanent" set-ups. The gravel bed should be about two inches deep and provides biological and mechanical filtering. These filters should be "hydro-cleaned" (using a siphon that tumbles the gravel and removes the debris from the gravel) regularly. In the Phoenix area, air-stems not only build up a calcium deposit, but also become home to a gooey bacteria that plugs the air flow. Be sure to use undergravel filters with easy-to-remove and clean air-stems.

    Some aquarists use undergravel filters in large "grow-out" and breeding tanks. Instead of running undergravel filters across the entire bottom and then covering them with gravel, they keep the bottom bare. As a filter, they use low, flat, circular goldfish bowls. Inside the bowl they place an round undergravel filter and cover it with gravel. For breeding purposes, spawning mops are placed over the gravel. Species like Blue Gularis lay their eggs in the mops.

    Sponge filters: These are probably the most popular filters in smaller set-ups. Like undergravel filters, sponge filters provide biological and mechanical filtration. The sponge provides a "nursery" for micro-organisms known as infusoria and these can be an excellent first food for newly hatched killie fry. The drawbacks to sponge filters are again clogging air-stems and the danger of trapping fish under the filter (some killie-keepers silicon-cement marbles under the filter to keep it raised). These are best used in bare bottom breeder tanks from two-gallons to maybe ten-gallons.

    Box filters: These are an old aquarium stand-by - and they still work. The filter materials can be lava rock, gravel, sponge, filter wool (or floss), activated carbon, ammonia-neutralizing crystals, or any combination of these (as well as some others less commonly used). While primarily used to mechanically filter the water, box filters can also provide chemical and biological filtering. Box filters offer flexibility through a choice of materials. They also tend to be bulky and somewhat of a visional eyesore. Air-stem clogging is also a problem. These are most suitable for two-gallon to maybe ten-gallon tanks.

    CHAPTER 3 - Good Beginning Killies

    What is available -

    Finding killifish can be a real challenge. If you check your local tropical fish store, you will occasionally find a few killies. However, it is the rare store that has any selection. The most commonly available killies are:

    1. The American Flag Fish (Jordanella floridea): is a native of Florida and is an unusual killie that will sometimes act like a cichlid, defending territory or a spawning site. The Flag Fish is a very attractively colored fish that is somewhat chunky and can reach four inches. This very hardy species requires at least a 10-gallon tank and, in Arizona, will thrive in a large pond.

    2. The Blue-fin Killie (Lucania goodei): another Florida native, but one that is seldom intentionally purchased by an aquarium store. This species often accompanies plant shipments from Florida (as eggs) or can be found as part of a Ghost Shrimp shipment. This is a slender, peaceful killie that reaches about 1 1/2 inches. The Blue-fin Killie tends to be very plain in store tanks, partly due to being young fish. Color is variable throughout its range and some locales can produce stunning fish.

    3. The Golden Wonder Killie (Aplocheilus lineatus): is a golden color morph of a killifish native to India. Lineatus can grow to 5 inches. They have a pike-like shape and are surface-dwelling fish. They are best kept at temperatures in the high 70 or low 80 degrees Fahrenheit with other similar-sized aquarium fish.

    All three of the above species are fairly easy to keep and can make nice additions to your collection of fish.

    Where do I find other killies?
    The above three species barely scratch the top of the iceberg as far as killifish go. Many hobbyists will see pictures of gorgeous killies in aquarium magazines and books and wonder where to obtain them. There are a number of sources:

    First, you will want to find out if there is a local aquarium society in or near your town. In Phoenix, you have both a general aquarium club, the Dry Wash Aquarium Society, and a club specializing in killifish, the Arizona Rivulin Keepers. Local breeders are your best source of both killies and information on how to succeed with them. If this is not an option, then check out the American Killifish Association at AKA members receive a monthly bulletin with a list of people buying and selling killies. All listers agree to abide by the AKA

    Code of Ethics.
    A third source is checking for killies on-line. You will find individuals who offer killies through their personal websites. You will also discover commercial sites such as AquaBid where you can participate in auctions. With these sources, let the buyer beware...

    What killies should I first obtain?
    There are a number of killifish that are considered to be excellent beginner killies. The list below is not intended to be complete, but rather provide some suggestions:

    1. The Gardneri Killie (Fundulopanchax gardneri): is actually a large complex of closely related sub-species, found mostly in Nigeria. Most are fairly easy to keep and breed. Perhaps the easiest Gardneri is the population from N'Sukka (or Nsukka). All Gardneri grow to a little over two inches and live three to five years. Some are feisty; others like N'Sukka tend to be relatively peaceful. Gardneri tend live near the bottom to the mid-water level, are eager feeders and will accept most foods, including flakes. Most Gardneri are bottom-spawners that prefer to lay eggs in bottom mops, plants like Java Moss, or in a substrate (gravel or peat). The notable exception to this is the N'sukka population. They seem to like to lay their eggs near the top of a floating mop. Gardneri eggs require about two weeks to incubate. Several populations, Rayfield and Jos Plateau, may be better incubated in a plastic bag in damp peat over a three week period.

    2. The Firethroat Flattop (Epiplatys dageti): is a two-inch pike-like killie with vertical bars from Liberia in western Africa. Males develop an orange-red throat and have an extension on the bottom of their tail - a sort of mini-sword. This is a very peaceful top-dwelling fish that accepts most foods and lives three or more years. Dageti (pronounced Duh Jay EYE) will lay eggs from the top to the bottom of a floating mop. The eggs hatch in about two weeks. The adults do not predate their eggs but will eat the fry. The only drawback to keeping Dageti is that you tend to produce more females than males.

    3. The Chocolate (or Golden) Lyretail (Aphyosemion australe): is native to the coastal rainforests of Gabon and perhaps the Congo. This species has been a long-time aquarium favorite and is available in several color morphs, as well as recent wild collections. Body colors can range from a rich chocolate to orange to reddish. Maximum size is a little over two inches and their lifespan averages 3-5 years. Males can develop attractive extensions to the top and bottom of their tail fins. The Lyretail is usually a very peaceful killifish, generally inhabiting the lower and middle levels of an aquarium. They will accept most foods. They lay eggs in plants or mops and the eggs incubate in about two weeks. Some strains of the Lyretail are easy to breed; others can be very difficult. Whenever possible, check with the breeder to find out how they were successful.

    4. The Two-striped Killie (Aphyosemion bivittatum): is another long-time favorite. This is actually not one species but a large group (called Chromaphyosemion) of related species where there have been a number of recent name changes. The group includes Bivittatum, Bitaenitiatum, Loennbergii, Splendopleure, Riggenbachi, Poliaki, Lugens, and several undescribed species. Bivs and Bits, as they are called, tend to be surface-dwelling killies that grow to about two inches and live from 3-5 years. The dorsal and anal fins of the males of some populations develop long extensions. Bivs and Bits spawn in plants or floating mops. The eggs hatch in about two weeks. Some of the more popular locations, such as Aphyosemion bitaenitiatum "Ijebu Ode", are easily breed in Phoenix water. Others, such as Riggenbachi, appear to require softer water just to be kept alive, much less spawned.

    5. The Guentheri Notho (Nothobranchius guentheri): differs from the above recommendations because it is an Annual killifish. In nature, this species lives where the waterholes dry out. Guentheri lays their eggs in the soil at the bottom of the ponds where they incubate during the dry season. When the rains come and the waterholes fill, the eggs hatch and a new generation repeats the cycle. Guentheri are found in Tanzania in east Africa and grow to about two inches. Whereas the previous four suggested fish are cylinderical in shape, Nothos are deeper bodied. In the aquarium, they can live beyond their natural lifespan. A frequent recommendation is to add a teaspoon of salt per gallon as a Velvet (a disease) preventative. Most aquarists breed Guentheri in a bare tank with a container with some peat in it. The peat is removed every one-two weeks, partially dried, and stored in a plastic bag (ziplock works well) for two-three months. Upon adding water to the peat, the eggs hatch out.