by John Mangan
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 livebearers.
"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 submissive coloration.
During this time the fish were kept well fed with small feeder goldfish. About once a week aprox. 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 fish.
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 4–6 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 canibal then seems to double his size overnight (this isn’t much of an exageration), which makes it easier for him to eat his next victim, and so on until all of a sudden you’ve gone from over 100 1/2" fry to 2 or 3 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 non–live diet, but the big question was, will this keep them healthy enough to breed? The answer is 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 freeze–dried bloodworms. Like they’re 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.