Article © Christophe Girardet, uploaded January 01, 2002.

All images by the author

Introduction

Exclusively coming from Rio Xingu, in the river rapids of Altamira, Pará, Brazil, Hypancistrus zebra is clearly a river fish. Keeping them properly is best achieved in a species only aquarium. The tank should be as long and as deep as possible; although they are deep-water fish, its height is not that important. To keep a six to seven strong colony of Hypancistrus zebra, you should at least give them a 80 x 40 cm tank around 100 litres.

The Rio Xingu biotope is well documented on the Internet. Hypancistrus zebra are tolerant fish in terms of their husbandry, but as the aim is to maintain and why not, breed them, you're best to give them the best conditions possible. It seems they're doing well in water with a bit less than pH 7, temperature between 28-30 °C. The water and particularly the bottom (H. zebra is after all a bottom dweller) of the tank must be very clean and filtered by a powerful system. A canister filter with a turnover of around 5 to 8 times total tank volume per hour is optimal to achieve the correct level of water treatment. At the opposite of the tank, you can add a 1000 l/hour power head to create maximum current. Feel free to adjust the current as the tank is laid out. But in any case, you must check that there are no "dead zones" where food could accumulate out of sight.

In such a tank, i.e. one that tries to imitate a river devoid of plants, light is not very important. Yet you still have to use some lighting just to see you fishes (at least) and to simulate the day and night rhythm. The light shouldn't be too bright or on too long as there are no plants to steal food from the omnipresent algae.

For the bottom you can use fine sand and some river gravel. On this first floor, you can add some bigger stones, caves and drift wood. With these materials you can create the maximum number of hiding places for every member of you zebra community. Use a big stone or a large piece of wood to separate the tank in two territories. This is in case you should have enough fishes that develop a territorial community with two alpha males. Moreover, the more places they have to hide, the more they will show themselves in full confidence of the ability to retreat to a safe place that isn't already occupied.

To keep fishes in such conditions (no plants and in a relatively small volume of water), you'll have to be strict with your water change regime. I personally change 30% water each week with half city water (hard in my country) and half osmotic water. The point is to stay very regular (in temperature and conditions) between the new water and your tank water. I've observed that H. zebra don't like too much of a change in any way.

Sexing Hypancistrus zebra
In a shop, it's hard to even see the difference between a male and a female for several reasons. Even experts can be embarrassed by their inability to accurately spot the differences. Often this is because most of the time the fishes are too young to be sexed or are too stressed to behave normally. But, on sub-adult (6-7cm) and healthy fish, you can have a good guess at gender by following these guidelines:

Male

Female

• On either pectoral fins leading ray, the male develops some quite large "odontodes". Odontodes are teeth-like growths in this case looking like a series of tiny stalagmites running along the fin ray. You can sometimes see a thicker first ray on dorsal fin too. A mature and dominant male will present very short odontodes on his lower body, from behind the dorsal fin to the base of his tail. The female hasn't any of these. Sometimes a female can exhibit very short odontodes on pectoral fins first ray, but nothing like those of a male. That's why it's difficult to sex animals under 7 cm.
• Immediately under the male's eyes, there is another this time "moustache like" growth, let's call it these "facial odontodes". The adult male has a very long one (about 1 cm) where the female just has a kind of hole with just a tiny little beginning of a moustache.
• The general form of the head is more abrupt with the male. It looks like the nose of a Formula 1 racing car. The bones right above the eyes are sharper than on a female that has a more rounded head. You best can observe this feature from the side.
• A male usually seems darker than a female, as if the black was more present than the white stripes.

I personally have a community of seven fishes with a good male to female ratio. I have four males and three females. That's why I could observe different and "natural" behaviour. We'll see further on what that's all about.

Before buying a Zebra Pleco
Take your time to choose your fish. There are a lot of indications you need to have before buying a zebra. Good signs are, for example:

• The "robe" is very well defined. The black is dark, the white is bright. Dull grey stripes can mean the fish is very stressed but not necessarily in bad conditions.
• The fins are all deployed, sometimes with a blue tinge on dorsal, carefully check all the leading fin rays aren't broken or damaged.
• The fish must be quick, scooting around in jerky movements more than swimming.
• The best fish is the one which makes you mad because you can't catch it!

Bad signs are, for example:

• A red or rosy spot on the body. It almost always means an internal injury or infection.
• White stripes not bright but a shade rosy; the fish is weak and bad water conditions (NH3, pH problems).
• Starvation signs like a hollow, sunken belly or an eye withdrawn inside the socket.
• General lines of the fish not straight, like bones broken, or fins damaged or destroyed.
• A lethargic fish is a problematic fish.

Social Behaviour
One thing you must know about Hypancistrus zebra is that this fish is as territorial as a cichlid. They live in a community where every male defends his small territory and when you put them together in a "little" area, there will be fights. Fights continue until an alpha male emerges and from this moment, he will be the "only one" for the females, for the food, for the best cave, for everything.

Over a whole year I observed that this hierarchy is very often subject to challenge and contestation. I have seen at least three types of fighting. This happens when a new "alpha pretender" comes around the main spawning cave. There's an immediate reaction from the dominant male if he's not guarding eggs. Otherwise, the alpha male just takes care of his fry in the cave. That doesn't mean the pretender will be safe a few days later mind you.

Brief "side to side" fight The alpha male doesn't permit "pre-spawning" behaviour from another male on his territory. If another male tries his luck, it breaks into a fight and if the pretender tries to resist, you'll see a kind of ballet, very short, but brutal. Each male tries to capture his rival's head with his facial odontodes deployed. As soon as they "lock horns" they make big and sweeping moves with their entire bodies to inflict the most damage to each other. Usually these ripping movements are very short, not more than five to ten seconds and the winner stays in place, standing bigger and more enflamed than ever, as if to say : "I AM the boss, RIGHT !?!" The vanquished loser hides away and stays very calm for several hours.

"Showing off" and intimidation When two subdominant males are fighting for their place in the pecking order, it's relatively clam and you could say it is all just superficial showing off. But this engagement can last several hours. They don't go for each other as viciously as in a real fight. They just chase and weigh-up their opponent over a few hours usually causing a real mess in the tank. Normally this ends with a light injury on the dorsal or tail fins. Feeding live food seems to trigger these contests. It seems to excite them and put them a belligerent mood for fights and shows of strength.

"Pseudo spawning" with bad injuries The worst case is what I call "pseudo spawning", because, except with great and almost permanent observation, the aquarist won't immediately realize that there's a fight going on. The two protagonists can be very seriously injured, sometimes fatally. I witnessed this twice in the period between March and November 2004. The alpha male vacated his favourite cave for a few hours. Meanwhile the second male thought it was a good idea to come in for a visit and, why not, to stay. The alpha male came back and I only realized after 4 days, that it was NOT a spawn, but a serious fight. They were blocked in the cave one behind the other, and the alpha male was literally eating the second. You can see on the picture below the result after five days. Finally the alpha male released his understudy and I was very lucky to able to save him. This incident gives more proof (if more proof were needed) of the feeding habits of Hypancistrus zebra, they're definitely carnivorous.

Feeding Hypancistrus zebra
As it's a loricariid, you might think this species eats algae and wood or suchlike. It doesn't. Analyses of L046 stomach contents show it eats anything; particularly insects, aquatic larvae, little shrimps, fruits and even meat.

I'm lucky to live in a rural setting, next to a tiny river in a forest. So I try to supply my fish with live food as often as I possibly can. So, they are fed live black mosquito larvae, gammarus, daphnia, red worms and sometimes a bit of dry meaty pellets. I used to give them a discus food, but I saw that they prefer living stuff. Furthermore, you can see them hunting in the current, and believe me, that's well worth it.

Hypancistrus zebra work with the current to catch their prey. They lurk behind wood or a stone and suddenly "fly" out to fall on the prey with their entire body. Once the prey is grounded, they go backwards, always holding the prey under their body, until they can properly eat it. Once again, the alpha male is the first to eat and if your tank is too small, he won't let the others join in. That's why it's very important to create enough caves and to provide food in several places.

Breeding Hypancistrus zebra
Like with any other fish, you'll have to meet certain criteria to have a chance of breeding Hypancistrus zebra. It begins maybe with the only real difficulty: you must not only have a pair, but a whole community to give a better than good chance of finding the right ratio of males to females. When you see the actual prices at your LFS, you may find it's a nonsense to try.

If you can overcome this financial outlay and you find yourself with a colony of six to eight individuals, you'll still have to think about how to stimulate them. Overall, I would say there are four major requirements to obtain a first spawn: the food, the current, the breeding caves and the stimulation.

First of all, you have to feed your fishes regularly and to provide them with good quality, varied and a sufficient quantity of live food. Not always that easy.

Second, remember that Rio Xingu is a fast flowing river. You have to move the whole volume of water in your zebra tank and this partly depends on your tank configuration. I guess a good average is 20 times the volume per hour, half in filtering, half just in current.

Third, your fishes must be able to find some caves or spots where they feel safe to spawn. I personally use baked clay tubes as breeding caves and these only have one issue: size.

The cave must be just wide enough for the alpha male to enter but also to block the entrance with his body. It must be deep enough for at least the entire body to enter. I've observed that larger caves are often left empty because the male can't entirely obtrude others entrance to the tube. I observed that, in my population, that they prefer a cave that is a oriented slightly against the current. The entrance is not straight on to the current, but just enough to let a bit of water movement inside. I guess it helps the male to keep the tube clean and oxygenated.

Fourth, you must obtain the first spawn. I've heard about a lot of things possibly stimulating the fishes. I took a chance with the 'natural' process. I mean giving them all the food and conditions they need to 'get in the mood'. I simulated a changing of season. I begun by feeding them heavily with very rich food for a whole month (be careful with the water changes). Then I began the following regime:

1st day: Normal temperature 28°C. Switch the heater off and let the temperature fall to 22°C over two days.

3rd to 8th day: Stopped feeding, no more water changes and let the temperature stay at 22°C

9th to 17th day : Raise 1°C per day until 30°C and in the meantime give live food again, progressively more over time.

18th day: Water change of 50% with similar water (as explained above)

If the first spawn is sometimes difficult to obtain, a mature female will lay eggs, in good conditions, every four to five weeks. This information is crucial in your choice of population. Indeed, as the alpha male is the only one the females would choose, if you have more than 2 females, your male will soon be exhausted.

As I write in early 2005, my alpha male is actually in uninterrupted spawning and guarding conditions from March 2004, at a cycle of one spawn every two or three weeks. Each of my three females court him all the time. That means he often has, in the same cave, a clutch of eggs, a few fry from two weeks earlier and another female, waiting for him to let her in.

This production line has several consequences. First of all, as he can't leave for taking a rest or simply eating, he sometimes eats a part of the eggs. I never saw him eating fry. Second, as he is exhausted, he lowers the quality of guarding fry, which causes a greater fry mortality rate in the first fortnight of their existence.

Normal Breeding
If you have the perfect colony of H. zebra, and a bit of luck too, you'll soon observe the following behaviour. First of all, the male will choose a cave that he will clean of all sand, gravel or detritus he will find. He uses his body as a tool to extract all the unwanted substrate from the tube.

Once the cave is ready, the male goes inside and simulates the ventilation of an imaginary spawn with his fins. He creates a light current with this ventilation and this behaviour alerts the females that he's ready. The alpha female positions herself around the entrance of the cave and waits for the male to let her in. After a time, the male lets her enter and follows her in thus blocking further entrance with his whole body.

He stimulates the female with very light shivers of his whole body in brief repeated sequences. After a while, the female answers with the same behaviour. This "nuptial" sequence lasts from one to four days, depending on the preparation and maturity of both partners. During this time, they do not feed or leave of the tube.

Depending on water and tank conditions, the female will lay bigger or smaller clutch of eggs. In very good conditions, she will lay up to 18 eggs in a clutch (this is the biggest spawn obtained by my population to date), but those eggs will be smaller. In less good conditions, she will lay a smaller clutch but the eggs will be bigger and rougher. This is, of course, not a rule, but just an observation made on more than 20 spawns in a year.

As soon as the eggs are laid, the female is expelled and the male begins the guarding phase. He makes then real ventilation with his fins and, almost all the time, manipulates the clutch of eggs with his mouth. He cleans them and eats the infertile ones. The time to hatch is between four to seven days, depending on the temperature and the conditions.

Even after hatching, the male will guard the larvae, cleaning and aerating them. A new father will probably loose a few larvae in the current of ventilation. Those have virtually no chance of surviving without ventilation or at least some parental care. On a tank with a sand and gravel substrate, you'll find some tiny predators: snails!

In fact, the larvae of Hypancistrus zebra have such a big yolk sac they can't move on normal ground. They are immobilised between pieces of gravel and become very easy prey for snails. You have a few choices here.

1. Let them die
   Can you really assume to loose the 90% of your first zebra spawn, just to educate this new father ? I couldn't.
2. Artificial care
   As soon as you see the hatch, you can probably take the larvae with a pipe and lay them in a specific nest, but you'll soon discover that without the attention of a father, they catch infection and die. You can take the whole cave (with male and eggs) and put them in a protected nest in the same tank. The problem is that you stress the male who may decide to eat the spawn. Moreover, extracting the tube, you will change the hierarchy and when you will replace the male in the tank for another cycle, you risk to interrupting the spawning, because of this change I have tried to take the clutch of eggs and to lay it in a very well aerated nest by an air-stone, but if the result is better, I still have a lot of dead fry. Too many.
3. Bare bottom
   A third solution is to let the whole process play out in the tank, but on a bare bottom. That's not a bad way but natural selection is aggressive too and you often can't find or take pictures of your babies.

Growing and Going On
The larvae arrive very quickly at the juvenile stage. During the first two weeks, the larvae will take 1 mm each day, living on their yolk sacs. Between, the 15th and the 18th day, the yolk sac is consumed and there is a critical phase : the digestive system requires the juvenile eat by himself.

I've tried several types of food for those young appetites. You can start with microworm but I've observed that they don't know when to stop eating and sometimes, they die of too much food. Personally, I use SERA Viformo tabs imbibed with red mosquito larvae juice (yuck!). One tab per ten juveniles twice daily (morning and evening).

Thereafter, the growth rate reduces a bit and you'll have to wait till the end of week three for your babies to reach 20mm. After four weeks, he will be around 23mm and after three months, he'll be around 30mm. Except accident, your fry is safe after this first month and will be OK until reaching 4.5 cm after a year and more or less, depending on the food quality and quantity, and at six to seven cm at two years old.

So now, you just have to try it!

There is further information on this species on the Cat-eLog page.

Back to Shane's World index.