Author Topic: Maintaining Killies  (Read 2976 times)


  • Administrator
  • Jr. Member
  • *****
  • Posts: 90
    • View Profile
Maintaining Killies
« on: August 14, 2012, 10:08:07 PM »
General Maintenance This information is from the American Killifish Association's "Beginner's Guide" at

In general, killies are kept in small aquaria, often as small as 2.5 gallons. For breeding, in particular, small tanks are preferred. Besides allowing closer observation of the fish, small tanks allow the aquarist to separate pairs and trios of different species. Most killie enthusiasts soon acquire several species, and we may as well mention here that, for the purposes of breeding, it is essential that different species, and even different strains, be kept strictly separate. Closely related species can breed and produce hybrids, but serious killie keepers strive to maintain different species in the "pure" state. Furthermore, hybrids may be infertile. Obviously, tank size must match fish size and larger fish, like Fundulopanchax sjoestedti (the Blue Gularis) require 5 or 10 gallon tanks. Larger aquaria, for example 10 or 15 gallon, or even larger, are used also for raising young fish.

As will be discussed later in this document, fry are often hatched in smaller containers, such as plastic "shoe boxes" or other storage boxes. In a typical fishroom for killifish, therefore, you will usually see tanks and containers in a wide variety of sizes. How these are arranged is a matter of personal taste, but killie fishrooms often have racks of tanks with small breeding tanks on top and larger rearing tanks below. One advantage of a fishroom is that the whole room, rather than individual tanks, can be heated.

Plants and Aquascaping
Planted tanks are pleasing to view, and plants help to utilize organic wastes produced by the fish and, to some degree, in oxygenating the water. However, many killie keepers avoid the use of plants in breeding tanks, and even in rearing tanks. Plants can make the collection of eggs, described later, difficult. Furthermore, bottom spawners may spawn in the gravel substrate, which is may be undesirable. On the other hand, one technique for spawning the "plant spawners" involves the use of a permanently planted tank and some breeders spawn bottom spawners over gravel. A common compromise is to use bare breeding tanks, and planted rearing tanks.

What plants to use is a matter of choice for the aquarist but, because killies often do best in tanks with relatively low lighting levels, plants tolerant of low light conditions are best. These include the cryptocorynes, Java moss, and Java fern. If gravel is used as a substrate it usually should be of a type that will not harden the water. A quartz sand or fine gravel favored by aquatic plant enthusiasts is #3 blasting sand, available at many hardware stores.

Many killies, such as the Aphyosemions, come from forest streams that are protected from direct sunlight, and prefer subdued lighting. In brightly lit aquaria, plants may provide some shading for killies that prefer low light conditions. Many killies appear at their best when light falls from above and to the front of the tank. Because of this, many killie enthusiasts illuminate their tanks, especially breeding tanks, by ceiling lights, with fixtures over only those tanks where more intense lighting is required.

Aeration and Filtration
Small aquaria, such as are often used for housing killies, are more easily polluted than large aquaria. The relatively small volume of water easily accumulates waste products, generating ammonia and nitrites, which are extremely toxic to fish. Most killie keepers, at least in the United States, therefore utilize some form of aeration and filtration. Air driven filters provide a home for aerobic nitrifying bacteria, which break down the harmful ammonia and nitrite to nitrate, a much less toxic end product.

Various types of filters can be used, but for small tanks the most popular are simple box filters, containing filter "wool", or sponge filters. Both provide a large surface area for bacteria to colonize and filter particulate matter from the water. Sponge filters have the advantage of not entrapping fry, a potential problem with box filters. In larger aquaria where a substrate is being used, under-gravel filters may also be used.

Ideal water temperatures vary depending on the species, but for most killifish the temperature should be in the range of 72-75 F. Conventional aquarium heaters may be used, but because serious killie keepers have several or many tanks, it is common for the whole room to be heated. Another advantage of this approach is that tank covers do not have to accommodate heater cables. Many killies are great jumpers and will exit the tank, and this life, through such small openings. The killie fancier, therefore, must ensure that tank covers are closely fitted.

Water Conditions
It is impossible to generalize about the water conditions required by killies. Some, such as A. cameronense come from soft, acid waters, while others come from harder, alkaline waters, and others from brackish waters. Some killies must have particular water conditions. Others, such as Nothobranchius species, can tolerate a range of water conditions. Naturally, no fish should be subjected to sudden changes in pH and hardness.

The pH of water, or a solution, is a measure of the concentration of hydrogen ions (H+) expressed on a negative logarithmic scale. Pure water is neutral, having a pH of 7.0. Acidic water has a pH less than 7.0 due to an increased hydrogen ion concentration, while alkaline water has a pH greater than 7.0. In both cases the change in pH is due to dissolved substances in the water. It is useful to have some means of testing the pH of the aquarium water. This may be done with test kits using indicator solutions, with pH papers, or most conveniently with an electronic pH meter. Small hand-held, battery powered pH meters are now available for relatively modest cost. Fish should never be exposed to sudden changes in pH. Thus, fish being newly introduced are usually acclimated by slowly mixing the water of the new environment with the "old" water.

The pH of water may be changed using weak acids, such as sodium biphosphate (NaH2PO4) or weak bases, such as sodium bicarbonate (NaHCO3, or baking soda). It is easy to change pH excessively using these chemicals, and the pH change produced may not be stable. A better way to reduce pH is to filter the water through peat moss. The peat moss is best boiled and rinsed then placed in a box filter between layers of filter wool. After a day or two the water will be amber and somewhat more acid. To increase pH it is best to include some form of calcium carbonate in the tank, such as a lime sand or gravel. Carbon dioxide (CO2) released as a waste product by the fish dissolves in water to produce carbonic acid, which will react with calcium carbonate to produce soluble calcium bicarbonate. The latter provides buffering capacity, helping to stabilize the pH of the water in the aquarium.

Water Hardness
Water hardness refers to the amount of calcium and magnesium salts, chiefly chlorides and sulfates, in solution. Hardness is measured in Degrees of Hardness (dGH) or as parts per million (ppm). It is common to see two types of hardness discussed, permanent hardness (calcium and magnesium salts other than bicarbonate) and temporary, or "carbonate" hardness (calcium and magnesium bicarbonate). The latter is a measure of the buffering capacity of the water, as previously discussed. Hardness can be measured using titration methods, and kits are available to measure both of these forms of hardness. However, for most purposes the conductivity of the water, as measure of total dissolved salts, is adequate. Small battery powered conductivity meters, which measure total dissolved salts in ppm, are available for this purpose. In most cases, the hardness of water is not as critical as pH. Water of 120-160 ppm is satisfactory for most killies, although there are some species that do best in very soft water, and some that do best in hard water. Water that is considered too hard can be diluted with rain water or artificially purified water. The latter can be produced using ion exchange resins or RO units. Ion exchange resins exchange sodium ions for calcium and magnesium. RO units remove calcium and magnesium ions through a process of filtration. Good RO water, therefore, is similar to distilled water. In recent years small, reasonably priced RO units have become available for use in the aquarium hobby and are seen in many fishrooms. Fish moved from hard water to soft should always be slowly acclimatized.