Keeping Motoro stingray in aquariums

Introduction - Origin

They are to be found in a wide area of South America occupying the large waterways that run through countries such as Colombia, Argentina, Brazil and Peru where they can survive in large numbers thriving on the excellent conditions that these waters provide for them.

They are often sold as juveniles but they do grow to a large size, adult males can reach a body diameter of up to 36 inches (~92cm) in the wild. In the aquarium the disc size will be slightly smaller but as you can see small aquariums are totally out of the question for this fish.

As mentioned above their markings can vary a great deal and this will include some slight colour variations, in recent years more variations are appearing as commercial breeding is producing some slightly hybrid specimens so always check where your stingray originates from and it may be best to purchase from a specialised breeder.

One word of warning, they do have a sting in their tail and should always be handled with respect, they possess a spine at the end of their tail that will sting if they break the skin while lashing about, in the wild this is purely for a defense mechanism, aggression towards the keeper is virtually unknown and the sting is more painful than dangerous. This usually happens when bad handling of the stingray is performed.

Another unusual feature that the Motoro stingray has is the ability to breathe while resting on the substrate, in this position the gill plates are covered but they have developed openings behind their eyes, these are known as spiracles which kick in and pump water down to the gill plates.

Caring for Potamotrygon motoro

As mentioned in the section above these fish can grow large and develop a large diameter to their disc, as a result the minimum aquarium size for these fish should be at least 8 feet (240cm) in length, they will also require room to turn around so the width of the aquarium should be at least 3 feet (90cm). The depth is not as crucial dependant on which tank mates they have, a depth of 2.5 - 3 feet (76 - 92cm) is sufficient but as you can see these are not cheap fish to keep so make sure that you have the means to supply them with a proper home before you purchase one.

The Motoro ray is a very active fish so keeping the aquarium as plain as possible may be the best option, this will also make keeping the aquarium clean much easier. Use sand for the substrate and supply a decent depth as they do like to bury themselves occasionally. Keep the lighting to a medium level, when first added to the aquarium it may be wise to dim the lighting until they settle in.

In the wild they inhabit slower moving waters so keep the water flow to a medium rate by careful positioning of the filter outlet pipes and they are classed as high waste producers so make sure that the filtration system can cope with the waste levels. It may be wise to go for a system that is actually rated higher than the water volume that the aquarium holds.

The water temperature should be set between 24 - 26°C (75 - 80°F) and the pH of the water should be slightly acidic although they will tolerate a neutral pH level.

Maintenance of the aquarium can be hard work, large water changes are required each week, regular water changes of 10% weekly is not enough for these fish, make sure that at least half of the water is changed weekly to keep the quality high. A tight fitting lid will need to be used as they are known to come out of the water when feeding.

They must definitely not be housed with smaller species of fish, they will prey on them. Many sites suggest keeping them with Arowana fish and this seems to work well.

Always make sure that the aquarium is fully cycled before adding the Motoro ray to the aquarium, they do not tolerate sudden swings in the water parameters. They are classed as a hardy species but they will still require optimum conditions to lead a long and happy life.

Feeding Potamotrygon motoro

In their natural habitat the Motoro stingray is a natural predator of other fish species and they also vary their diet with crustaceans or other invertebrates that are available. To keep these fish in optimum health it is advised that the diet is varied but they will require a meaty diet throughout. Other commercial foods can be offered but these should be not used as the staple diet so you may need to keep a good stock of foods available either fresh or frozen. If using frozen make sure the feed is thawed out completely before offering them to the fish.

Younger specimens are fine if they are fed on the usual live or frozen foods such as blood worms, artemia or tubifex but they do have a ravenous appetite and will need feeding a couple of times per day. They are very active and can burn off their food very quickly.

More mature specimens will obviously require larger feeds, a good method is to offer cockles, mussels, whitebait or prawns. When first introduced to the aquarium they may be a bit shy of feeding but they do need to eat as soon as possible to keep their health in top form.

Some keepers in the past would offer feeder fish but this practice is on the decline, not only has it fell out of favour but it also increases the chances of introducing diseases or infections to the aquarium.

Always make sure that your ray has a healthy appetite and shows no signs of loss of body fat as this could be a sign of problems with your fish.

Breeding Potamotrygon motoro

Breeding is definitely possible with Potamotrygon motoro but as with the housekeeping should not be attempted unless you have the means to care for any offspring properly. To sex these fish is not a major problem, only the males possess claspers on their pelvic fins, these are used to grasp the female and pass over the sperm for fertilising the eggs. The claspers can be seen at quite a young age so purchasing a group of juveniles will not be required to get both sexes.

Purchasing a male and female will not guarantee getting a mating pair but is probably more practical than housing several specimens. One important aspect is the size of the adult fish, the males can become very aggressive towards the female when spawning so it is wise to use a larger female compared to the male. Courting can be quite a physical affair with the male harassing the female constantly and if she is not ready he may even bite the female so be prepared to separate them if necessary and try again a couple of weeks later. If the female is ready she will allow the male to slide below her with their bellies touching, he will hold the female with his claspers and pass the milt into the female, this procedure is over very quickly and once complete the male will detach himself away from the female. Motoro stingray produce fully formed live young, these are known as “pups”. Nature has found a way of feeding the offspring while inside the mother fish, when first hatched the young will feed off the yolk sac but for further nourishment she has developed glands in her uterus that supplies milk to feed up the pup. Gestation can take up to 12 weeks, this is a long period when breeding fish but when the pup is released it is fully competent to take care of itself and the normal practice is to remove them away from their parents and raise them separately.

Like most young fish, they require a lot of nutrients to keep their growth rate high, they will require feeding several times per day on live or frozen feeds as mentioned in the feeding section above. To keep the water quality high you should also perform regular water changes on a daily basis to begin with, this can be reduced to a weekly water change as the pups start to increase in size.

Carrying pups can be a stressful and tiring time for the female so do not overdo any breeding project and allow the female time to rest for a few weeks after a couple of batches of pups.