Belenesox belizanus, The Pike Livebearer
by John Mangan, PVAS
From Delta Tale, Potomac Valley Aquarium Society
Belonesox belizanus is the only member of its genus and is a relatively large
for a livebearer, predatory fish. They can be found from southern Mexico through much of
Central America and have also become established in the U.S. in some parts of Florida and
Texas. They prefer shallow, slow moving waters where they hide in plant thickets and wait
for their prey.
One look at an adult Belonesox is all that is needed to recognize it as a
predator. The fish is torpedo shaped and has a small dorsal fin set well back on the body
for speed, and large sharp teeth for grasping prey. They also have a perpetual
"snarl". This is due to the somewhat unique shape of their mouth which aids in
holding onto their prey.
Belonesox is a Poeciliid and, like the related guppies, platies,
swordtails, etc., is very easy to sex since the male has a modified anal fin (gonopodium).
They also spawn, and give birth to live young in generally the same way as the more common
"So", you may be asking, "what's the big deal about raising Belonesox?
They're just big guppies." In some ways this is true, but can you imagine an 8"
female guppy swallowing a 6" male? I don't mean killing him and eating him bite by
bite, I mean swallowing whole. With Belonesox this is very possible, and not at
all uncommon. I've lost four full grown males this way. The first two were victims of one
large female who was then banished to solitary confinement. I then obtained two more pairs
which were set up in a well planted 30 gallon tank. The tank had an air operated outside
filter and temperature was kept in the mid 70's. Most of the literature on this fish
recommends the addition of some salt to the water, some even go as far as to say that the
fish will not breed, and in some cases even live, without this. However, I have found salt
to be totally unnecessary.
Everything went well for quite some time. The males and females seemed to get along,
fry were produced about once a month (more on this below) and the only aggression was
between the two males. One became dominant and developed a lot of golden coloration in the
throat and abdominal areas. The subdominant male could be identified by a broad black
stripe down his sides, similar to juvenile coloration. I was able to tell that this
coloration is due to dominance by removing the dominant male and having the other one
"color up". When the dominant male returned the other one went back to the
During this time the fish were kept well fed with small feeder goldfish. About once a
week approx. 20 goldfish would be dumped into the tank. Unlike oscars or other cichlids,
which would eat (or kill) all 20 within five minutes then lay around with a stomach ache
for 3 days, the Belonesox would eat one or two apiece and then slowly eat the
others one or two at a time over the rest of the week. Everything seemed to be going along
very smoothly until I ran out of feeder fish for a few days. Since everything had been
going so well I didn't worry much about it. I brought home a bag of goldfish when my new
shipment came in and dumped them into the tank as usual. The two females rushed out of the
plants and each grabbed a goldfish, but there was no sign of the two males. I didn't think
much of it since it was quite common for any number of the fish to be back in the plants
and not visible. The next day I glanced into the tank, saw the two females but not the
males, still didn't worry. Next day glanced in again, still no males in plain sight. Now I
begin to worry a little bit, but just a little. I still thought they must be back behind a
plant leaf. I decided to take a closer look. After much searching there was no sign of the
males. The lesson here: If you want to keep Belonesox don't run out of feeder
While I'm on the subject of feeder fish every article I've read about Belonesox
talks about feeding them guppies. Don't waste your time and money trying. I can't imagine
trying to keep my adults full on guppies, even being able to get them wholesale. I have
several 2" juveniles I've kept to raise as my next generation of breeders which can
each eat 2 or 3 average size feeder guppies per day. I'll let you try to figure out how
many it would take to satisfy an 8" female.
After all of this, if your still crazy enough to want to raise Belonesox, you
need to be told, or should I say warned, about raising the fry. The female Belonesox
can give birth about every 46 weeks, and can easily have well over 100 fry per brood.
Pregnant females do not have to be isolated from the others. Well fed Belonesox
will not eat their fry. The fry are about 1" at birth and have a dark stripe down
their sides. The fry will hang motionless in the plants and will resemble small sticks or
pieces of debris. The first time I saw one was while making a water change. I tried to
suck up a piece of dead plant and to my surprise the "plant" was trying to swim
away from the siphon. There is no big hurry to remove the fry from the parents tank ( if,
as I said above, the adults are well fed). As an experiment I've left a number of fry in
with the adults for about a week before they finally got eaten, and that was because I ran
out of goldfish.
Sounds easy so far, doesn't it? Well here comes the hard part, feeding the fry. The fry
are born hungry. The best food I've found for the fry is brine shrimp. By this I don't
mean baby brine like you feed to those wimpy little cichlid fry, I mean adult brine
shrimp. Daphnia is the next best, if you can raise enough, and you need LOTS. The fry eat
enormous amounts of food and if they don't get it they eat each other, actually even when
they do get it they often eat each other. I've seen a baby Belonesox eat another
one the same size. The cannibal then seems to double his size overnight (this isn't much
of an exaggeration), which makes it easier for him to eat his next victim, and so on until
all of a sudden you've gone from over one hundred 1/2" fry to two or three 2"
fry in an amazingly short time. You can slow this process by separating the fry by size
often. You need very sharp eyes though. It's very common to have one large cannibal find a
dark corner or other hiding place where it sits very still so you don't notice it until
there are no other fish in the tank.
The only time I've managed to raise most of a spawn up to over an inch was when I fed
them lots and lots of adult brine shrimp. I then sold them to a local wholesaler (don't
count on doing this though as there is a very limited market for Belonesox). They
will also eat Daphnia, as mentioned above, mosquito larvae, newborn guppies (an entire
brood of guppies from a large female is just an appetizer though for a brood of
Belonesox)and some will even eat flake food. Growth on flake food is extremely slow
though. As the fry grow they graduate to larger and larger guppies, then finally goldfish.
Belonesox aren't for everyone, but they are possible to spawn and raise if you
are willing to make the commitment to give them what they need. Which means, in other
words, that if you want to raise Belonesox you should be committed.
I have to go now. There's two guys here that keep insisting I try on this funny looking
jacket, even though I keep telling them that the sleeves look way too long...
AUTHOR'S NOTE: the above is a slightly revised version of an article
originally published in April 1988. Being the type of person that doesn't let the fact
that I should know better stop me from doing something, I am now keeping Belonesox again
after several years of not having any. Below are my new experiences with them.
I decided I wanted to try something different this time by seeing if I could avoid
using live food. I placed a pair of Belonesox in a 70 gallon tank which was
already occupied by a very large true gourami (Osphronemus) and a very large eel.
The tank was unplanted and the pair stayed mostly at the surface of the water and mostly
together. Since they were by far the smallest fish in the tank they probably stayed
together for a feeling of security.
This pair of fish were full grown, wild caught adults. They, therefore had probably
eaten nothing but live foods their whole lives. I had very little trouble getting them to
start eating freeze dried plankton (the large size zooplankton). At first I had to make it
appear to be moving a little by throwing it across the surface a little bit. This probably
made it resemble a large insect landing on the water. After a relatively short time though
they learned to go after the plankton even if it was laying still on the surface.
Now I knew that I could keep them alive on a nonlive diet, but the big question was
would this keep them healthy enough to breed? The answer was yes. Since they were in an
essentially bare tank which contained, in addition to the two fish mentioned above,
several large Callichthys cats and a very large raphael cat, most of the fry were
eaten in spite of their camouflage. I was able to find six of them and moved them into a 2
1/2 gallon tank. I started out feeding them Daphnia for about the first week or so. Since
there were only six of the little monsters I didn't have much trouble giving them enough
to keep them full. I also put several gravid female guppies in the tank with them. As soon
as they were big enough I began trying to wean them to dry foods. I would give them a meal
of Daphnia in the morning, to be sure they didn't get hungry enough to eat each other, and
in the evening I would give them some freezedried bloodworms. Like their parents at
first they would only eat it if I dropped it into the bubbles from their filter so it
looked like it was moving. Also like their parents they learned very fast not to care if
it was moving. I then stopped all live foods and now feed only the bloodworms.
The fry are now about 2" long and living in a 5 1/2 gallon tank. I still have all
six. Nobody ate anybody else, which really surprised me in the small tanks they've been
kept in so far. The fry would probably have grown much faster on a diet of live foods but
I believe they have become better "pets" this way. When the little Belonesox
see me coming towards their tank with the bloodworm can, they get "excited" and
come rushing to the front of the tank to be fed. The next question I want to find an
answer to, is can I raise these six to adulthood and get them to breed on a dry food
diet? Maybe in another five years I'll reprint this article again with another addition
tacked on and give you the answer.