Keeping and breeding Hypancistrus zebra (L046) – Part 2: Breeding

See also Part 1: Keeping Hypancistrus zebra
Zie ook deel 3: Raising the Fry

Introduction

If you wish to breed the fish, the obvious place to start is the composition of the colony. Various views have been discussed over the years as to what constitutes a good breeding colony. It is generally accepted that one should go for less males than females, either one male with two females or 2 males with 5 females. My own experience with plecos is that numbers are not of crucial importance. Clearly, the more males / females a colony has the more chances there are for a spawn, provided that there is adequate space and spawning sites for all. My preferred colony composition, if I have a choice, is 3 males with 5-6 females, though on occasions I had spawns from colonies with a different composition (like the Hypancistrus zebras, as it happens). In general I would prefer more than two males for a number of reasons. Firstly, it creates a kind of “competition” between them – thus giving the males the incentive to spawn and the females a dominant male to be attracted to. Secondly, It gives the females a choice. Thirdly, it minimizes the chances of ending up with one male who cannot or does not want to spawn. Finally, if something happens to one of the males there are still another two in the colony to carry on. I get more females not just to ensure there is competition, reproductive ability and choice; females may get locked in a cave and die in the process of reproduction.

Sexing the fish may be tricky if they are not yet sexually mature. There are certain characteristics that are good indicators towards correct sexing. If looked from above the wider heads of the males are clearly noticeable. Similarly, if the underbelly is examined, males have a V shape at the end of the genital area while females a U shape. Sexually mature males have pronounced interopercular odontes (spikes at each side of the head); similar spikes, though not as long and thick, can occasionally be observed on females who are referred to as “hairy ladies”. Again, the first pectoral fin ray of sexually mature males is thicker than this of the females and usually adorned with spikes. Some very helpful photos for identification can be found http://www.l46.de/Geschlechter/geschlechter.html

Left: Photo of sexually mature female (left) and male (right) Hypancistrus zebra as seen from above for sexual identification. Source: <www.L46.de.

Above: The interopercular odontes and the spikes on the first pectoral ray of a mature male.

Another indication of sexual dimorphism mentioned quite often is the shape of the pectoral fins. Males are supposed to have long and straight pectoral fins as opposed to females, whose pectoral fins are shorter and have a half-moon shape.  Though this may be the case with a number of individuals it cannot be taken as a general rule. A piece of advice: sexing can be quite difficult even for experienced pleco keepers. The characteristics indicated above will help in identification if sexually mature individuals of both sexes are available for comparison. However, this is often not the case. If in doubt try to get advice from experienced zebra keepers.

Above: a pectoral fin which extends like a straight line is often taken to be an indication of male sex.

Above: the V shape can be clearly seen in the genital area of a male fish.

Once the colony is selected I let them settle and get used to sharing a tank. I generally try to avoid upsetting a colony with new introductions at this stage. I have, on occasions, introduced a new member to a tank just when I am trying to breed the fish only as a “shock” factor, i.e. when the colony is not breeding as a way of kick starting it. In some instances this worked, in others not, so I can’t tell if it is effective.

During the settling in period avoid disturbing the colony. Don’t change the decoration, caves, wood etc every other day. If you make a change, give it 2-3 months at least to see if it is effective.

I am assuming that you know about your fish and the water and other conditions in the tank are within the appropriate range for them. At this stage you need to watch your colony carefully. See how the fish behave, where they go in the tank, what times they get in and out of their caves, which areas in the tank they avoid, if any, and so on. Change the layout appropriately to make sure that all the inhabitants are perfectly happy with the tank environment and that the males have settled in their caves. Once everything is fine my experience is that within the next 6 months the colony will spawn.

Patience is a virtue and with zebras this is more so. Females mature at 3 years of age or thereabouts whereas males take a year longer (at least this is what is currently believed with regards to wild caught fish). There is no point trying to rush your fish to spawn by the traditional “wet-dry” simulations and such like; if, however, you are so inclined, you will find a very detailed account of various things to do in Kristian Adolfsson’s article “Dry and Rainy Seasons in the Tank It is important to remember that the fish want to spawn; they are programmed genetically to do so. The aquarist does not have to force the fish to spawn; it is preferable to remove any barriers to spawning – and there are plenty of barriers preventing the fish from spawning in an artificial environment, such as a tank.

I am a firm disbeliever in feeding the fish well prior to spawning. The fish should be fed well all the time; keeping your fish in good condition will promote spawning and this cannot be achieved by changing their diet a month prior to your preferred spawning date.

A final word of caution: don’t add anything to the tank (plants, wood, fish etc) once you get to the final period before spawning. The last thing you want is a disease outbreak.

My first zebra spawn

Getting my colony to spawn was quite easy though some may see it as an exercise in patience. My Alpha male, Caesar, had been with me for 4 years while the last addition to the colony joined the tank a year and a half prior to the first spawn. During this time I did not try to spawn the fish; I first let them grow in the 1200 lit tank, then I moved the colony to a 250 lit dedicated tank. The colony consisted of 19 individuals, 10 males and 9 females, of whom 12 were adults (i.e. over 3 years old).

• Tank specs: 122cm x 46cm x 46 cm (l x w x h); total volume 258 lit,
• Substrate: Aquarium sand (quartz)
• Pumps: two Blue Modular internal filters (1200 lit / h each)  attached to one side of the tank, one with a spraybar attachment and one with the normal nozzle, both with venturis. With regards to the water turnover in the tank it should be noted that the performance of all pumps deteriorate with time. On paper, the turnover of this tank is slightly under 10 times per hour; in reality it is 5-6 times per hour. The flow under the wood and rocks where the caves are is considerably slower than at the top of the tank
• Aeration: One Tetratec APS 400-600 lit with two outputs, each in either side of the tank.
• Furniture: a big central piece of bogwood which is arching quite high in the middle of the tank, providing shade for the fish to move under; a row of 5 caves at the back of the tank, separated by formations of slate, beach stones and wood; a row of 2 caves at the front of the tank placed directly in front of the empty spaces of the back row; smaller pieces of bogwood ether side of the front row; arching pieces of bogwood at the top with Java fern and anubias. Floating ceratofyllum demersum..
• Lighting: A twin Arcadia lighting unit (55W).

It is worth noting a couple of things on the tank furniture.  All the pieces of wood in this tank are “plec friendly”; they have plenty of cracks and little holes for fry and youngsters to hide in. Similarly the slate and rock formations can be used as temporary hide outs or permanent areas of residence by youngsters up to 6-8 months old. Organising things like that in advance helps when the fry arrive in that the aquarist can avoid interventions which will upset the colony. The plants are also useful hiding places for youngsters while keeping the water clean. Ceratofyllum in particular is extremely effective against nitrates while also providing a nice shade. Finally, a word about the caves: there are three different types of caves in the tank. One type is made of clay (the caves measure 9x4x3cm) and the other two of slate. The slate caves all measure (10x3x2.5cm) except one cave in the front which is 10x3x2cm (internal dimensions, l x w x h).

Youngster hiding under a piece of slate. Great care is required when removing the tank furniture or the internal filters for maintenance. There could be the fry hiding there which may fall outside the tank (or, even worse, end up down the drain). Place a net under anything which is being removed from the tank and put tank furniture and filters in a clean bucket to double check that there are no fry attached to them.

When the fish got in the tank I noticed my Alpha male, Caesar, going straight for the back right hand corner cave. The second male also got himself a cave at the back while my third male, Zeus, got in the first cave of the front row – this is the narrower of all the caves. This cave is situated only 5 cm inside the front glass and is hit directly by all the current and the sunlight of the window facing the tank. I was surprised Zeus didn’t get to the back row as there were plenty of caves free there but I assumed he was going to relocate later.

For a couple of months all the fish, with the exception of Zeus, moved around. The back caves were temporarily occupied by the younger males or by females. Zeus stayed put in the front cave, which I found surprising. Four months before the spawn Zeus and Caesar, who was passing by as it were, had a tiff just outside this cave and Zeus managed to get Caesar off it. This was absolutely unbelievable and I should have known at the time that something was afoot.

I waited until Christmas was over and decided to start “preparing” the colony for the spawn. Given my travelling commitments February and March seemed good months to have a spawn. The added advantage was that during these months it is usually raining in Manchester, which would be helpful if low atmospheric pressure is necessary for the fish to spawn). At the third week of January I stopped all water changes. The tank lighting period was already on “winter time” (during winter the tank lights are on from 11 am to 9 pm; in summer this changes to 9 am to 12 pm). I raised the temperature by one degree Celsius (from 27^oC to 28^oC) and kept raising it for 3 weeks, until it reached 30^oC. I changed the diet of the colony only slightly: they were given twice weekly frozen bloodworm instead of their usual once weekly treat. I also stopped adding bicarbonate of soda and Discus mineral salts so that the pH and the GH could get slightly lower. Finally, I reduced the flow of the pumps to the absolute minimum (one thing I like about Blue Modulars is that they have an adjustable flow system).

During the second week the pH crushed; the reading indicated a value of less than 3. The fish looked ok but I got worried, so I started adding soda again. I gradually raised the KH to just under 3 which brought the pH fluctuating between 7.2 and 7.6. I kept an eye on Caesar’s cave but there was not a lot of activity there. Much to my surprise I noticed my lead female appearing more and more often near Zeus’s cave, right at the front. Zeus, however, kept blocking the entrance of his cave and wagging his tail every time she was approaching, indicating he was not in the mood for a visit.

Blocking the entrance of the cave while wagging his tail, the male clearly indicates he will not allow the female inside.

After a few days of careful watching last thing at night and first thing in the morning I realised what the problem was. The light from the window was hitting directly into Zeus’s cave. I added a piece of bogwood over Zeus’s cave to shade the entrance, drew the curtains and kept them drawn since.

Four weeks after I stopped the water changes I performed a massive water change with fresh water which lasted just over two and a half hours (continuous flow). The new water was 27^oC. I added bicarbonate of soda and 5 ml of Esha Optima, cleaned the filters and returned the flow to high. The water from the pumps was hitting the surface of the tank water, thus creating maximum movement and oxygenation. I repeated the same thing twice, every two days. On the 7th day I raised the temperature to 28^oC again; one day later I noticed Zeus was stuck in his cave and was not coming out to eat. I checked with a torch and I saw, to my absolute delight, that he had the female locked in.

From top to bottom: Zeus’s female, Lady Godiva, patiently waiting under Zeus’s cave to be accepted, until she is eventually allowed inside the cave. Center image: Caesar pushing against his female to help her release the eggs.

While the female stays in the male blocks the entrance of the cave with his body and won’t let her out until she is ready to release the eggs. This can take anything up to four days. I was determined to keep calm but could not do so. In the days that followed I kept checking at least two or three times daily, using the torch, which annoyed Zeus immensely. The female stayed in for 3 days; when she was allowed to exit, Zeus was fanning eggs.

As this cave is the one most hit by the current, the sand tends to get carried away and as a result the cave is slightly leaning forward. There was therefore a danger of the egg ball falling outside the cave. I inserted a small pebble under the cave to keep it straight. Zeus indicated his displeasure by wagging his tail wildly as my hand approached the cave but there was no harm done. This fish has proved, time and time again, that he is an excellent father.

Zeus stayed in the cave for about 15 days; as the cave has quite a narrow opening which was entirely blocked by Zeus’s body it was impossible to see what was happening inside.  Eventually, against my better judgement, I succumbed to the temptation of checking on Zeus. George lifted the cave upwards and looked in with the torch to see Zeus guarding one of his fry.

George and I discussed the next steps at length and eventually decided to place the cave in a breeding trap inside the main tank; the plan was to wait for the dad to leave the cave for food and get the youngster. In the meantime, we placed another cave at the same spot Zeus’s cave was prior to it being relocated to the breeding trap. In the days that followed a number of things happened:

1. Caesar got in the new cave which was placed at the location Zeus’s cave was and spawned straight away.
2. Zeus remained inside his cave in the breeding trap, so eventually we had to drag him out and put him back in the main tank. The location where his cave had been previously was now occupied by Caesar fanning his eggs, so we put a new cave in for Zeus at a nearby location. Zeus didn’t go near it. He kept going in circles around the location of his old cave, which Caesar was now occupying.
3. The youngster disappeared from the breeding trap a day later and I can only assume that he joined his father and siblings in the main tank (youngsters can jump pretty high in the water).
4. Zeus re-took possession of the cave that was put in the location his cave was as soon as Caesar moved out to eat. However, he was not very comfortable with this cave (the entrance is slightly taller). So we replaced this with his usual cave. He got settled straight away and spawned again 6 weeks later.
5. Interestingly enough, though he clearly wanted “his spot” back, Zeus did not challenge Caesar while he was fanning eggs. He waited for him to get out of the cave and then moved in himself. Caesar did not fight to get the cave back (at least I didn’t see a fight and there were no signs of one).
6. Caesar moved back to his old cave and has kept this location (and cave) since, spawning once every couple of months.
7. Hermes, my Beta male, spawned within a week from the other two, followed by a fouth male a week after that.

Top image: Caesar guarding eggs. The fish positions his body in a way that shields the eggs entirely so they cannot be seen from the outside. Normally the fish would be further out, tending the eggs with his mouth. On this occasion he felt the cave moving as we were lifting it to take a photo and moved as close to the eggs as possible to protect them with his body.

Center image: Zeus guarding newly hatched fry. One of them has left the protection of the father, which is why it is important to have the cave tipped slightly backwards, so the youngsters don’t fall outside.

bottom image: Zeus guarding newly hatched fry. Most of the fry ran to hide under his body when they saw the flash but we were lucky as one of his youngsters was not particularly bothered by it.

From the facts indicated I made the following observations:

1. The fish didn’t mind the spawning location so near to the front of the tank, neither did the usual commotion (photos, us walking by to feed or service the tank etc) put them off from spawning.
2. The fish preferred to spawn at a location close to the current. This observation is reinforced by the fact that Zeus, the occupant of the cave closest to the current, is the most regular spawner; other males who occupy the caves at the back (which are protected from the current though there is still some movement there) are not as good spawners as Zeus. We are currently planning a new layout for a zebra tank to check this observation out, as it could well be that Zeus is just exceptional. Having said that, my experience with other Hypancistrus points to the fact that a certain amount of current is important for them to spawn.
3. The Alpha male is not necessarily the best spawner in a colony. In our case, the Alpha male was not the first to spawn neither is he the most regular spawner. Similarly, the Alpha male has not tried to harm other males who spawn or attack their fry (we have read a number of reports to this effect on the internet).
4. I have often heard that no more than two males from a colony will spawn in the same tank; I have evidence to the contrary. Four males spawn regularly in the tank and there has never been an attempt from any of them to disturb the others. They have taken possession of particular caves and they just stay in their caves or move around them, clearly avoiding the territories of other males.
5. The fish (in this particular case Caesar and Zeus) knew very well were their “own” territory was. Further, in Zeus’ case we have evidence that the fact his cave got removed, then put back at its usual location, did not put him off from future spawns, as is often argued.
6. Surprisingly, there have been no territorial fights between Caesar and Zeus, or any of the other males. This could be a possible indication that the fish are used to living in close proximity but occupying their own space. Provided such an option is available territorial fights can be avoided (it is important to note that Caesar, Zeus and Hermes, amongst others, are all wild caught individuals).

Subsequent Spawns

The colony is spawning regularly since the first spawn. Water parameters seem to be unimportant in that we have had spawns in winter (27^oC) and in the summer (29^oC-30^oC), straight after a water change or just before one is due, even during holiday periods when due to absence there are no water changes for 2-3 weeks. On the main, the KH is 3-4, the GH is 5-6 and the pH 7.2-7.6. The flow varies, obviously, but it is considerably slower than what it was during the first spawn mainly due to the performance of the pumps which naturally deteriorates over time. The colony has been offered frozen foods twice during the last year because there are usually fry present in the tank. This doesn’t seem to have had an effect on their spawning activity.

Males seem to spawn at different intervals. Zeus remains the top spawner; Caesar spawns once every couple of months. The others spawn irregularly. After a sequence of spawns the colony seems to take a break for a while (2-4 months), then they all start again.

The size of the egg ball varies, depending on the female. 10-20 eggs will be laid each time however not all will become viable fry. I usually get 7-15 fry per spawn.

Zeus is the best father in the colony. He has never eaten the eggs despite the fact that he has occasionally been under quite a lot of stress. Caesar has only eaten the eggs once, after we removed the top of his cave to take a photo. On all other occasions he took excellent care of both eggs and fry. Hermes eats the eggs as a norm. He is easily stressed and I try to make sure, when I see him locking his female in, that there is minimum movement around the tank as well as no interference (not even water changes) whatsoever. Even so, there are no guarantees that a successful spawn will take place.

Zeus is the one that will take best care of his young. He allows the youngsters to stay in the cave for long periods of time (six to eight weeks is not unusual with him). I don’t know if any fellow aquarists had a similar experience so I will report one more fact which I have not seen reported anywhere else: if Zeus wants to spawn and he has some of his fry from a previous spawn still in the cave he will get them out while the female goes in to lay and then accept them back in. Time and time again we have seen him with eggs and fry from a previous spawn in the cave, as well as fry from a new spawn together with older fry from a previous spawn. None of the other males do that.

Top image: Zeus guarding fry (left hand corner, under his nose) while a youngster from a previous spawn is seen over his head. Bottom image: Fry from two spawns (clearly different in sizes) are inside Zeus’s cave while he is out eating.

It is quite easy to know when a spawn will take place by looking at the females. When the females are ready to spawn, they will go and sit on top of the cave of their male (Zeus’s female used to go under his cave, where the pebble made some space for her. We have noticed that and put an arching piece of wood over all the caves. The females now go and sit under these pieces of wood.). The males will either wag their tail fast, indicating they will not accept them in, or will move sideways. The latter is an invitation. Females are usually around and on top of the male’s caves 2-3 days prior to spawning.

Spawning sequence: the female on top of Hermes’s cave; the female enters the cave; the male “pushes” her to release the eggs; the male guarding eggs.

On the odd occasions a different female tries to spawn with a male, World War III breaks in the tank. I have witnessed more fights between females protecting their “relationship” with a male than between males (who in the case of my colony are pretty calm and indifferent to each other’s presence in the tank).  It is quite interesting to see how fast a female will appear next to the cave of her male when another female tries to occupy the space on top of his cave!!!

Fry grazing around their father’s cave..

Fry are well aware of the location of their father’s cave and will run inside for protection when they feel threatened. Every 2-3 months we take the wood, slate etc out to collect the fry and put them in a separate tank to grow. Regardless of where they are in the tank when this happens, fry will set off for their own father’s cave, rather than getting in the first cave near them.  They will hide under wood and slate on the way but will not attempt to enter a cave occupied by a male other than their own father.

Fry are collected from the main tank to be put in a grow out tank..

The colony’s spawning pattern does not appear to be affected by the elimination of frozen food from the menu. This has been necessitated by the presence of fry in the tank for long periods of time.

Author: Marina Parha

See also Part 1: Keeping Hypancistrus zebra
See also Part 3: Raising the Fry