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BASIC CARE OF KILLIFISH

 

Basic Care and Maintenance

To begin, conditions for individual species may vary and this is an overview to give good starting point for the majority of Nothos. In the section dealing with individual species, I have attempted to identify the specific conditions necessary for some of the more sensitive fish.

AQUARIUMS

Although some members of the group are relatively mild mannered, Nothos should not be considered a community fish. In nature, it is uncommon to find Nothos inhabiting the same waters as most other types of fish. Occasionally, when the rivers overflow during the seasonal rains, some barbs, characins, small cichlids and other species are washed into the pools and ponds that contain Nothos. Lungfish are sometimes found inhabiting the same waters.

In nature, (based on observations and presentation comments by Dr. Brian Watters, Dr. Barry Cooper) male Nothos tend to be regionally territorial, staking out areas near thick plant growth and enticing the females to approach. Females tend to swim in the more open waters of the pools. When ready to spawn, a female will seek out an attractive male. Some studies have indicated the intensity of color draws the female to a male.  This attraction may indicate a strong need to identify the strongest genetic line.

There is some speculation – particularly in South American annuals – that color attraction occurs primarily in younger fish. When the fish approach the end of life, females then tend to seek out less vibrantly colored males.  It is noted early in the reproductive process, the fish tend to lay their eggs along the edges of the pools – possibly indicating eggs which require a longer (or shorter) incubation period – while the eggs later in life tend to be laid in the middle of the pool.  The obvious comment is the edges have already dried and the later spawns are simply down with the passing of time.  The question remains – does the position of the eggs play a part in extended dry periods or does it hold some other biological meaning?

Plant growth is thicker and closer to the edge of ponds, areas which are shallow and dry first. In the rare cases where the water does not completely disappear, the edges of the pools still will be dry and the eggs will incubate in those areas. This actually may be more common in South American annual species. It would be interesting to follow the behaviors of the fish in the wild from hatching to reproduction to death to gain a better understanding of the natural progression of aging and how it plays into the long-term survival of the species.

There are definite differences between breeding and maintaining Nothos in the home environment and the type of aquariums that should be considered. Although the specifics will be discussed under the spawning section, a ten-gallon tank appears to be a good choice for a breeding set-up. Certainly, Nothos can be bred in smaller tanks with good success. There are a number of breeders who prefer a five-gallon aquarium.

Maintenance is considerably different. The first and perhaps the most important step is to separate the genders. Nothos are continuous breeders. That is to say, if a female is near, the male will attempt to entice her to spawn.  If he is rejected, then he will drive off the female.  This constant pattern of continuous pressure on the females can cause the females to seek safety. They will have a harder time feeding and often will become thin and the production of eggs slows. Step one then, is separation of the males and females.

The size of tank chosen for maintenance should obviously be based on the number of fish. Keep in mind, there will be several steps in maintenance from newly hatched fry to adult fish, however, a good rule of thumb for space is one dozen fish (12) per ten gallons of water. This allows room enough for the fish to continue to grow. While females tend to be compatible, males often attempt to establish dominance and will spar. If there are only two or three males in a tank, you may want to consider separate quarters for each. Without a doubt, one male will become dominant. If you are maintaining larger numbers of Nothos in a single tank, then a balance is usually found. (On a personal note: I have found that a 20-gallon high tank is a nice size for maintenance even for fewer than a dozen males.)

Vegetation: Since plants provide important cover in the wild, vegetation is very useful in the artificial environment. A combination of floating plants (watersprite, hornwort) and potted plants (broad-leaf swords, cryptocorines, java ferns) creates an attractive environment, provides hiding places and builds security. In addition, it is much simpler to move potted plants when there is a need to remove fish from the tank. Plants also have the added benefit of being an indicator of the overall health of a tank.

WATER CONDITIONS

Readings taken by various collectors demonstrate some disparity in the overall water conditions in the wild. What we do in the home aquaria may be considerably different than the conditions found in nature, but over many generations and decades of experience by numerous hobbyists, certain factors seem to remain constant for a majority of species. The hobbyist should be cautious in applying the general conditions and may wish to check the individual species descriptions to gain more specific information.

Since annual eggs hatch in nature when the seasonal rains fall, we know the TDS (total dissolved solids) of the water is very low if not non-existent during the early stages of the initial hatches and lifecycle (note: Studies by Dr. Brian Watters on the AKA Email List KillieTalk have indicated that while the initial rainfall is less than 10 TDS, within 24 hours, it rose to over 100 TDS.).  Most reports of the rainfall indicate a slight acidity. Over time, the TDS will increase and the pH will also change according to the local conditions. Initially, the rise of the water table will bring groundwater with additional mineral content into the pools mixing with the rainfall that originally filled the ponds resulting in an increase in the TDS. In some areas, rivers overflow their banks to fill the temporary ditches and culverts, affecting the overall properties of the water. As the cycle continues and moves into the dry season, evaporation and the lowering of the groundwater boosts the TDS and the dying of vegetation can lend itself to changes in the pH values.

An additional factor which may affect Nothos in the wild include the region the fish are found. In Malawi, most of the biotypes are affected in some way by Lake Malawi, a hard water habitat with a pH over 8.0. Despite the high pH (Watters, Nothobranchius: Habitats in Malawi, JAKA, 1991), the majority of habitats tested demonstrated a moderate pH range of 7.1 to 7.4 and a TDS ranging from 50 to 120 ppm. He did indicate a couple specific sites that were outside that range. Interestingly, he used the alkaline water directly from Lake Malawi in holding tanks for his collection without any apparent negative affect on the fish. That water had a pH of 8.1.

In 1999, a British expedition covered considerable ground in Southeastern Mozambique and a number of the collection locations measured a much lower pH ranging from below 6.0 to 6.6. Again there were variations and in at least three locations the pH measured 7.5-7.6. Perhaps even more interesting, the TDS was below 100ppm in nearly all cases. However, one location ( MOZ 99-11 ) reportedly (Wood, British Killifish Association Killi-News Jan. 2002) contained a TDS reading of 470ppm and a pH of 7.0.

While these are interesting indicators for the home environment, there appears to be a different approach taken with most Nothos. It is interesting to note that many breeders have great success using conditions that seem considerably different than in the wild. The following water conditions are by no means required, but instead reflect some generalized comments based on those used by numerous hobbyists. Without question, some species require specific conditions for long-term successful propagation.

TDS: It is interesting to compare the TDS of the home environment with the reported conditions in nature. The vast majority of hobbyists agree the TDS should be above 150ppm and some use an even higher concentration.

pH: The recommended pH of 7.5 or higher seems to be a common preference. High readings of over 8.0 have been used without negative results. However, there are some species (N. robustus) which seem to prefer more acidic conditions.

Temperature: Collectors commonly report water temperatures in the lower to mid-80s during the day, but many readings seem to find waters in the mid-70s. Nothos tend to seek out the shaded areas and water temperatures can be 2-4 degrees lower, but still reasonably high. This is likely important in nature to enhance the growth and reproduction rates to meet the short life cycle.

Since Nothos are short-lived fish in the wild and higher temperatures will result in a faster metabolism, most breeders prefer to maintain their populations at temperatures in the lower 70s Fahrenheit (21-23C). By using the lower temperature, the fish should survive longer, some species occasionally living as long as 18 months to two years.

In contrast however, breeding Nothos at a higher temperature appears to result in more reproductive activity. The majority of my breeding tanks average 78F to 82F. Based on personal experience, this may shorten a long-term breeding program, more eggs appear to be produced and fertilized. Many breeders report consistent success breeding Nothos at lower temperatures 72-75F and it appears to be a personal choice.

Salt: Possibly the single most essential consideration a hobbyist needs for healthy Notho maintenance is the addition of salt. One of the real health concerns for Nothos is the development of velvet, particularly in fry tanks where it is difficult to detect. Salt inhibits velvet and therefore is the single most important reason for its addition.

There are a variety of opinions and choices when it comes to adding salt to a Nothobranchius tank in both the amount and the type of salt used. Some breeders use a tablespoon of salt per gallon of water, while others prefer a teaspoon. Additionally, the type of salt used varies. Some prefer to use marine salts because of the included minerals, while others tend towards a kosher salt or a canning & pickling salt.

Two considerations are of real concern – iodized salt is an absolute taboo and the addition of baking soda to certain brands of non-kosher salts should be avoided. 

Water Changes: It cannot be stressed more the single most important factor to success with Nothos, and for that matter any fish, is to do regular water changes. Despite all of our advanced filtration systems, protein skimmers and chemical additives, the water needs to be changed on a regular basis to remove many waste products produced by the fish and plants.

Unfortunately, today’s community water supplies require so many chemical additives to meet state and federal standards, it is becoming more and more difficult to be able to use the old technique of letting water sit for 24 hours to remove the chlorine. Chloramines, fluorides and other additives from your local water treatment company last far longer than 24 hours – some may last weeks.

Some of the options available today to provide quality water can be expensive, although there are numerous commercial additives available to condition aquarium water, most are designed to remove chloramines and chlorines. Certainly those chemicals are among the worst in the short term and should be the first concern; there are other potential harmful conditions. Heavy metals, lead and copper poisoning can also cause difficulties.

Some hobbyists use rain water as much as possible and there is certainly a lot of positive things to be said about this natural source. Scientifically, rain water should contain no hardness and be of a neutral pH, but unfortunately the ideal does not exist. It is important to test the water regularly to determine the pH levels (particularly in the northeastern U.S. where acid rain is a serious problem). Be aware, as rain forms in the clouds, it can contain particulate matter from factories hundreds of miles away which affects the chemistry of the water. Pre-filtration of a large water storage system should be a standard with both carbon and good overall mechanical filtration.

In many areas, hobbyists find it necessary to use a reverse osmosis system to remove the majority of minerals and chemicals from their water supply. R.O. water is nearly pure, a neutral pH and no hardness. While this method is probably the best mechanical option, the hobbyist also has to monitor the water carefully, mix in water to raise the mineral content and be cognizant of the buffering for pH.

 

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