Raising and Care of Belonesox belizanus

I first acquired these fish at one of our local fish store’s opening. They caught my eye because they were unusual and very rarely seen locally, and they looked big and mean. These fish could almost be in the same class as the bruisers of the cichlid world, but to my liking they are LIVE BEARERS. They come from Central America; specifically southern Mexico, south to the Honduras. They do very well in Calgary hard water and thrive in hot temperatures, as high as 35C. The females grow very long, and can go up to 20cm in length, with the males about half that size. So they need a large tank with good plant coverage and space to roam.

I bought two females and one male and happily put them in a 120-liter tank by themselves at around 25C. But to dismay they very quickly got some fungus growing on those very long, large mouths; and they seemed to be listless. So into the literature I went to find out anything I could about these fish, but very little could be found. So onto the Internet I went, and again the same lack of information. I decided to add some salt and up the temperature to 30C. Within a week all was well with the females, but I lost the male and the females looked hungry. The two females were sharing a tank with a large discus and didn’t seem to bother each other and both enjoyed the heat.

I tried to feed frozen foods, white worms, and all sort of other dry combinations but I soon learned that these females had already been spoiled with live feeder fish. Now I don’t like to feed using this method as I’m too much of a nature lover to knowingly put live fish into a situation where they will have no choice but to meat their maker. But after much deliberation I gave in and finally fed them their choice in life. Now I have been told that if you can get fry from day one you can train them to eat other (non-living) diets. Ah: a challenge for me to see if this is possible. I have already had this success with my oscars so let’s see if these bad girls can also be changed. That would mean starving them for at least a while, but this is risky, and remember I had lost the male and I didn’t know if my two females were pregnant. As with other types of large live bearing species that have monster fry, it is sometimes very hard to tell if the females are gravid due to their size and the way the fry lay lengthwise in their mother’s womb. So back to the Internet and the books to find out all I could about the breeding of my new live bearing bruisers.

Again very little seems to be written about how long it takes for them to give birth, or how they breed, or even if the females carry the males’ sperm for a number of months. I had two options: either spend more money on another male ($10.00 CDN); or wait and see. All right, everyone knows (because I’m the club treasurer) that I’m cheap. So next came the waiting game. One morning as I’m doing their morning feedings I notice these small, thin, stick-like objects floating around in the hornwort. Oh no, I thought to myself, I have leaches in my tank! Just look at them all…they must be from that darn fish store, right? Wrong! Well, guess what? They weren’t leaches… they were pike minnow fry and they were huge! At least 1cm to 2cm long. There were about 25 fry, all hanging out in the hornwort and dashing around very quickly every time I went near them. I did find some info that indicated that the females wouldn’t bother their own fry or eat them as soon as they were born. But looking into those hungry eyes I wasn’t taking chances. Out the fry came and all are happy.

A few days later there was more fry, from the other female. Again, there was around 25 fry from this second batch. Out they came too. Now these fry are in small show tanks (5 liters) and its time to test them out with other types of food. It did take a couple of days but soon they were eating frozen foods and white worms. They love to chase white worms around on the bottom of the bare tank. The next question to be answered was “do the females need a male to fertilize them again every month as do the goodeids, or do they carry the sperm packs for a few months, as do other poeciliids? I spent a long month waiting for these answers.

But back to the children. They did very well for over the month, but do to technical difficulties with Trans Alta Utilities and the electrical supply to my home, I lost one whole tank of fry and half of the other tank before we got back the power. BOO HOO. I also noticed that some of the smaller fry were loosing pieces from their tails and the larger fry had very fat tummies. Watch out! It looks like we have a case of big fish, little fish. So I started to feed more often and larger amounts and gave them more room to run away and hide.

The end of the month comes along, and low and behold I see another batch of fry, but this time only eighteen in number. So there is my answer: females do carry the male sperm for a few months, and don’t need monthly fertilizing as do goodeids. But much to my disappointment the second female hasn’t dropped any more fry, and now a few months later, both females are not dropping.

The fry are growing well in larger tanks. They are still being fed non-living food. Some interesting things about the original females are that they won’t eat anything but live food, no matter how long I starve them. They seem to only hunt and eat at night when the lights are off. Their hunting style is to hide in the plants at the top, then quickly dash out at the feeders, trying to grab one in one fell swoop. Sometimes they get their mouths full and sometimes they totally miss. But it seems that their hunting is a single hit or miss procedure, and they don’t worry about chasing the feeders or trying repeatedly to get them. I guess their attitude is that the feeders aren’t going anywhere, so we’ll try again in a little while.

Hopefully in a few months the fry will start breeding and I can continue to see if I can keep them completely off of live fish as food. There are some interesting black colorings on the tails of the fry. This could be the differences in the sexes when young, but as they grow older they seem to loose these markings. There already is a size difference showing, which is certainly indicating that the young females are starting to show their growth difference over the young males.

The two moms are still happily awaiting some male companionship and are easily sharing their home with the large discus. But be aware that anything small enough to fit into their large mouth is certainly fair game to them.

So if any aquarist would like to have one of the flesh eating, large mouthed, big bruiser type fish with an attitude, and are tired of the cichlid people saying “Ah, it’s one of those live bearers; you know, feeders for my cichlids”, just show them one of these big babies that look like alligators and a new respect for live bearers will certainly not be far behind. ?

Book Review: Aquatic Systems Engineering: Devices and How They Function

This is a review of the new CAS library book, Aquatic Systems Engineering: Devices and How They Function, by P.R.Escobal. The author is an aeronautics engineer that left the field to form the companies Aquatronics and Filtronics, manufacturers of “high-end” aquarium filtration, aeration, and sterilization equipment.

The book discusses the use of these items in setting up an aquatic environment: both single tank and multi-tank systems. The proper sizing of components is discussed in detail, and mathematical rigor is used. This book is therefore not light reading: in fact, tables, schematic diagrams, and calculation make up the bulk of the book.

The calculations are however complicated by the exclusive use of American Imperial units throughout the book, rather than the much simpler SI units. As the author is American, this is understandable, but even American engineers will nowadays calculate in SI and (if required) convert the result to antique units after it is found.

After an introductory chapter that defines the terms used throughout the book, the meat of the book begins with a surprisingly complicated discussion on how to determine the time required for passing all of an aquarium’s water through a device (such as a filter). The complication arises from the fact that the water from the filter is mixed with unfiltered water on return to the aquarium. It is shown that all of the water can never be filtered in such a set up, but 99.99% of it is effectively filtered after the volume of water is cycled through 9.2 times. One can safely round this to 10 times, and say, for example, that a 100-liter per hour filter would require 10 hours to filter all the water in a 100-liter tank. The commonly used aquarist “rule of thumb” is to use a filter that pumps the aquarium’s water volume two to three times per hour, reducing the filter time to about four hours.

The next chapters deal with the proper sizing and operation of ultraviolet sterilizers. It is here that the author shows his biases. Chapter three opens with the sentence “Fishwise, the single most important device available today, ranking second only to a well designed mechanical filter system is the ultraviolet sterilizer”. Even setting aside this statement’s self-contradiction, I find this declaration odd to say the least: the vast majority of successful amateur aquarists don’t even use an UV sterilizer so they clearly can’t be that important. And the mention of a mechanical filter I also find odd, because I only use them as a prefilter to my biological filter, which I would surely rank as the most important aquarium device anyone can have.

If the opening statement was meant to boost sterilizer sales then I am afraid that in my case, at least, it has failed, since the contents of the sterilizer chapters have convinced me not to buy one. The discussions on “dwell time” and “zap dosage” clearly show the futility of using a small UV sterilizer in a moderate to large sized aquarium system. For example, a 25-watt UV sterilizer (itself costing about $250) can only be useful on a 180-liter or smaller aquarium, and then only if the flow rate through the sterilizer were carefully regulated. My 500-liter show tank would require 64 watts of UV to be effectively sterilized at a cost of nearly $1000 (including pump, flow monitor, and plumbing). Since I have never seen any of the diseases that UV sterilization is supposed to prevent, this expense hardly seems justifiable. However, to anyone deciding on using an UV sterilizer, I would say that these chapters are required reading, as they convincingly demonstrate that careful matching of the tank capacity, sterilizer wattage, and pump flow rate is required for satisfactory results. You simply can’t stick any old sterilizer to the output hose of your canister filter and expect effective sterilization.

The following chapters discuss the design and operation of protein skimmers, and should required reading for anyone wanting to design such a device.

There is also a chapter that discusses heating and cooling of aquaria. Heat loss from a model aquarium is examined and examples are given as to how to determine the heater wattage needed for a given tank. This information is potentially very useful, but unfortunately it doesn’t adequately address all the complications that arise from extraneous heat coming in from the lights or water pumps, or the complex configurations of multi-tank systems, or of open-air tanks that suffer from evaporative heat loss. So in the real world, you would still probably have to rely on trial and error when sizing a heater for a multi-tank system.

Two points do however become quite clear while reading the chapter on aquarium heating: acrylic tanks require much smaller heaters than do glass tanks, and
“watts per gallon” heater sizing rules are useless. Heat is lost from the tank proportionally to its surface area, not its volume. So even though beginner books may advocate buying a heater big enough to supply “5 watts of heat per gallon”, and even though this may be fine for a 10 gallon tank (50 watts of heat), it results in serious overkill in 100 gallon tank, where 500 watts of heat will cook your fish.

The chapter discussing water pumps is also informative, but is hampered because it discusses pump performance in terms of output pressure. Unfortunately pump output pressures are almost never given for hobbyist pumps. Instead, pumps are rated by flow rate…either at a variety of “heads” (if you are lucky) or as a single value. The pump “head” is the height the water is lifted by the pump, but many aquarium pumps are designed strictly for “flat flow”, or zero head. Such “circulation pumps” are only given a passing mention.

For those pumps that are rated for pump flow at various heads, it is easy to determine the pump pressure, but the relevant equation is not provided in the book. So here it is…let

P = pump output pressure in Pascals.

z = be the height in meters where flow rate drops to 0 (the maximum head).

d = density of water (which is 1000kg/m3 for fresh water)

g = gravitational acceleration (which is 9.8 m/s2 near the Earth’s surface)

then P = d g z

= (9800 kg m-2 s-2) z

To convert pressure in Pascals to PSI, multiply the pressure in Pascals by 0.000145 PSI/Pa. You can also make a quick estimation of the pressure by remembering that every meter of head requires the addition of about 1/10 of an atmosphere of pressure, where 1 atmosphere is about 1000 Pascals or 14 PSI. For example, my pond pump is reported to pump to a height of 8 meters, so it must deliver about 11 PSI.

Once the pressure of the pump is determined along with the diameter of the pump outlet, the flow rate at any head is easily determined from the formulae presented in this book. But much more importantly, the book also presents the information required to allow you to design a real filter system, taking into account the losses of flow due to friction in your hoses and connectors.

This information is to my mind the most universally applicable information in the book, as the most complicated piece of “aquatic engineering”” that the advanced hobbyist is likely to attempt is a single-pump, multi-tank fish room. Everything you need to know about sizing and designing such a room is included in this book, and I don’t think anyone should attempt it without first having a thorough read. ?

What’s New In Cichlid Studies: Part 3

CICHLID SPECIES

Cichlidae is among the most speciose fish families in the world. Their diversity is especially wide in Africa. Zoologists are therefore understandably curious to know why this is so, and why the speciation happened so fast, since some of the great African lakes are less than one hundred thousand years old.

Among the obvious suspects is geographical discontinuity. Populations are more likely to differentiate into new species when they are confined to a small area and prevented from interbreeding with other populations. The barriers do not have to be absolute, as species will still develop even if there is a small amount of genetic interchange. This also applies to species developing as a result of specialising in different food types, where there can still be a bit of overlap in diet during speciation [6]. A third method of speciation, demonstrated in Lake Victoria cichlids [7], occurs when gender preferences for colour displays drifts apart. One group of males tends to prefer a certain pattern displayed on another group of females, another group a different pattern, and so forth. The incipient species may still interbreed, but as time goes by they can drift apart genetically into distinct species, purely on the basis of mating habits, not food niche or isolation. This is not a case in which a new species suddenly occupies one certain area, or eats only a certain food that no other cichlid does.

One stumbling block faced by zoologists is that first the researcher must determine what species are in the study area. It is seldom the case that there are clear and distinct fish. More commonly a continuum of populations exists where the fish at either end are obviously different but there is a gradual transition in between. Aquarists will receive the extremes of wild fish from collectors and think of them as distinct, yet someone who sees them in habitat will not be so confident.

Labeotropheus fuelleborni is a Lake Malawi cichlid kept by many aquarists. A study published in 1999 showed that this cichlid migrates readily enough along rocky shorelines, but more than two km of sandy beach or deep water will intimidate it and act as a barrier to gene flow. The study was carried out along the Nankumba Peninsula shoreline at the south end of Lake Malawi [1]. Males at the northwest end of the peninsula were darker blue with darker grey bars, while males at the south-east end were lighter in colour with stronger red-orange fin pigmentation. It can be seen that the fish are two extremes of a single species, but if isolated by geographical change long enough, they would eventually develop into distinct species.

In the aquarium, such extremes are often considered as two species. Against this, however, “interbreeding” in the tank has been common, especially where the females are drab and easily confused. A lost cause of the American Cichlid Association is its valiant fight to eliminate cichlid hybrids from the hobby. The danger of hybrids is that by muddying the gene pool they make it impossible to reconstruct the original species by line breeding. This never used to matter because aquarists could start over again with freshly imported specimens from habitat. Now in some cases those specimens are gone, because the wild species has been wiped out. The most prominent examples of this are the Lake Victoria cichlids, exterminated by the introduction of Nile perch into the lake.

AGGRESSION

Cichlids have a general reputation for being aggressive in the home tank, but I think this unfair. In habitat, aggression seldom leads to fatal consequences because the loser can flee the area. This is not possible in the aquarium. The two most common reasons for this are that the tank is too small and that the aquascaping allows one or a few fish to dominate the entire tank.

Just how much room is needed can be estimated from studies such as one carried out on Lamprologus ocellatus, a snail-dwelling cichlid. The male keeps a harem of females. He prepares empty snail shells, keeping one or two open and burying the others nearby for future use. The largest female will dominate the harem and will be quite intolerant of other females. In habitat, the females of a harem will establish themselves about 90 cm apart [4]. One can see that this would not be possible in the average home aquarium, but aquascaping to block females’ views of each other could allow a small harem. Otherwise the tank may only support a single pair of fish, rather than a harem. Whatever the case, it is easy to see that in habitat the snail cichlids have room to spread out, but in a small tank they end up killing each other because the losers can’t get away. From this is then made the claim that “cichlids are aggressive”. Confine six aquarists in a small utility room and see if they don’t become aggressive as well!

In the converse, however, it will not pay a cichlid to have too much territory, more than it can reasonably defend. A study on convict cichlids (Cichlasoma nigrofasciatum) showed that large cichlids defend food patches against smaller convicts, and experience a growth surge because of the better food supply. The food patch can be so large that the owner spends more time defending it against intruders than enjoying the benefits. As a result, the growth rate of the convict declines because it is using up too much energy [5]. In habitat, cichlids must obtain an optimal sized territory. Too small, and it won’t provide a living. Too big, and it will be indefensible. The cichlid must strike a balance between food and energy expended in defence. By extrapolation, in the aquarium, fish which spend most of their time defending territories are burning up energy which could be used for breeding. Something to think about when stocking a tank or wondering if it should be culled.

RAISING THE FRY

It is not unusual for parental cichlids to be guarding fry of other parents, or even other species. Some cichlids, such as the Tanganyikan Microdontochromis, actually release their fry into other broods not even the same species [2]. Lamprologus ocellatus females are known to accept other fry if they are not too dissimilar and are smaller than hers [4]. Smaller, because large fry will cannibalise small fry if the size difference is too great. For those aquarists who want to maximise their output of spawns, this suggests that fry should regularly be culled and sorted on the basis of size, to keep each group at about the same average size and thereby avoid cannibalism.

One might expect parents to resent such unwanted foster care, but, without being able to read the thoughts of a cichlid, there seem to be some reasons why this is tolerated. To pick out individual fry in a swarm is a difficult energy-consuming task, one which would also attract the attention of predators who would swim over to see what all that thrashing is about. (Predators are often attracted to thrashing because that may indicate a prey in trouble and thus easier to take.) The dilution effect reduces the chances of a parent’s fry being taken by a predator. If, for example, one-third of the cloud of fry are not the parent’s fry, then the odds are one-third that a predator will snatch someone else’s kid.

FEEDING

Mouth brooding cichlids normally don’t eat while carrying fry. This is not an absolute rule, as Microdontochromis is known to be able to feed and brood simultaneously [2]. The parent feeds on zooplankton floating through the water, and so do the brooded fry, thus enabling them to grow bigger and faster.

Aquarists dealing with a newly-obtained cichlid for which they are unable to find information can often determine what type of food it eats and how it eats by looking at the mouth structure. Aquarists often forget that it is important to know not only what type of food the fish eats, but how it eats. A mid-water feeder will ignore the algae growing on a rock, while the algae scraper depends on that food source. Algae biters have stronger jaws, such as the Lake Victorian haplochromine Neochromis [3].

Quality of the food makes a difference not only to the general health of the fish but to its success in territorial defence and breeding ability. It is common in many species for the female to chose a more brightly coloured male, all else being equal, because the pigmentation of fish depend on their diet. The better the diet, the brighter the colours. The brighter the colours, the better the male must be as a father. It isn’t just humans who judge by image!

This was demonstrated by a study on male fire-mouth cichlids (Cichlasoma meeki) where half the test fish were given a high-carotenoid diet and the other half a low-carotenoid diet [8]. The more carotenoid, the brighter the red pigment of the fish. The brighter the fish, the more likely it was to win aggressive interactions with other males.

REFERENCES

1] Arnegard, M.E. et al (1999) Population structure and colour variation of the cichlid fish Labeotropheus fuelleborni Ahl along a recently formed archipelago of rocky habitat patches in southern Lake Malawi. PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON 266B:119-130

2] Yanagisawa, Y., H. Ochi, and A. Rossiter (1996) Intra-buccal feeding of young in an undescribed Tanganyikan cichlid Microdontochromis sp. ENVIRONMENTAL BIOLOGY OF FISHES 47:191-201

3] Bouton, N., F. Witte, J.J.M. van Alphen, A. Schenk, and O. Seehausen (1999) Local adaptations in populations of rock-dwelling haplochromines (Pisces: Cichlidae) from southern Lake Victoria. PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON 266B:355-360

4] Brandtmann, G., M. Scandura, and F.Ttrillmich (1999) Female-female conflict in the harem of a snail cichlid (Lamprologus occellatus): Behavioural interactions and fitness consequences. BEHAVIOUR 136:1123-1144

5] Praw, J.C., and J.W.A. Grant (1999) Optimal territory size in the convict cichlid. BEHAVIOUR 136:1347-1363

6] Genner, M.J., G.F. Turner, S. Barker, and S.J. Hawkins (1999) Niche segregation among Lake Malawi cichlid fishes? Evidence from stable isotope signatures. ECOLOGY LETTERS 2:185-190

7] Seehausen, O., J.J.M. van Alphen, and R. Lande (1999) Color polymorphism and sex ratio distortion in a cichlid fish as an incipient stage in sympatric speciation by sexual selection. ECOLOGY LETTERS 2:367-378

8] Evans, M., and K. Norris (1996) The importance of carotenoids in signaling during aggressive interactions between male firemouth cichlids (Cichlasoma meeki). BEHAVIORAL ECOLOGY 7:1-6 ?