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Freshwater Stingrays and how to care for them

Articles on general fish keeping

Freshwater Stingrays and how to care for them

Postby Mick » Wed Dec 09, 2009 12:18 pm

Freshwater stingrays have become increasingly popular in the aquarium hobby over recent years. They are now widely available in quite a few aquatic stores but not all that much information is displayed on how to care for them properly. The are often kept in tanks that are far too small for them and another common mistake is keeping males with a female of the same disc diameter, this will inevitably lead to the female being injured. Hopefully this article will provide some basic care tips and provide information on this beautiful family of fish.

Motoro Stingray

The Origins of the Stingrays
It is beleived that this species of fish have been evolving for 300 million years making them some of the oldest species on the planet, they have changed very little and there is still scarce information about these fish in their natural habitat. Most of the freshwater ray species are found in the Amazonian River Basins although there some inhabitants in unconnected waterways of South America. Most of the species for sale today belong to the Potamotrygon family and these are suppossedly very closely related to the Marine species of rays. It is beleived that they became trapped in the South American water ways when the Andes mountain range suddenly rose about 15 million years ago blocking off the water ways from the Atlantic Ocean. The climatic changes forced the trapped rays to evolve quickly to cope with their new surroundings which they have done with great success. They have learned how to cope with sudden drops in the water levels duriong the dry seasons and can be observed basking in the shallow water in groups which are known as "dormitories". When the rains re-appear they disperse and at this time it is very difficult to track them due to the hazard nature of the rivers at this time.

In many regions they are caught as a food source, in some areas they are even classed as a pest and killed, the carcasses are just left to rot away or for scavengers to enjoy a feast. Economically this does not make sense as they hold a greate value if they are caught and sold into the aquarium trade.

Mosaic Stingray

Sting in the Tail ?
Before we proceed to the next section it is only fair that I must point out something that all ray keepers must be aware of, these fish can inflict a painful sting if startled or excited, always treat these fish with respect. On top of their tails towards the rear there is a serrated stinger, this is normally covered over with a layer of skin which can make it hard to see. However, if the fish is startled or feels threatened, the stinger will be uncovered and with a simple flick of the tail a cut can be inflicted. The stinger also contains a venom that will cause blistering and numbness in the affected area. The best treatment as it happens is to run hot water over the wound, this will neutralize the toxins. Always seek medical advice as soon as possible for further treatment. Always take care when performing tank maintenance or hand feeding the fish which is quite a common practice. The stinger is still active on dead rays so if removing a dead specimen from the tank, take care!!!!

Polka-dot Stingray

Setting up the Ray tank
Most specimens of rays for sale in the stores are juveniles but these fish grow very quickly and as such require a large tank, the minimum size that should be used for these fish is 6'x3'x3'. They require plenty of swimming space and can even swim to the surface to feed reaching out of the water if needed so ensure that a lid is fitted to prevent them from leaving the tank completely. The choice of substrate is either sand which is the best option, fine gravel (rough gravel can damage the fish), or leave the substrate out completely and have the tank bare bottom which is the choice of some keepers as it makes tank maintenace a lot simpler.
The heater can cause problems in itself, these fish burn easily so either fit a guard to prevent the fish from touching the heater or use an inline heater that is mounted from the filtration system. The setting should be between 22-30 degC and it is best to spread the heat by using at least two heaters, this will also prove to be a life saver should one of the heaters break down.
The water needs to be slightly acidic, in the natural habitat the fish live in very soft, acidic water containing very few minerals. They are very intolerant of high ammonia and nitrates, this can lead to organ failure, particuarly the kidneys so these must checked on a regular basis, if the tank is mature and good husbandry is performed, this should not be a problem.
They are high waste producers so the filtration system needs to be able to cope. With the larger tanks it is best to either run a sump system or use two external filters, these will need to be cleaned on a regular basis also. To keep the water quality high it is best to perform two water changes a week, at least 25% each time.


Otorongo Ray

Feeding your ray
One of the joys of keeping stingrays is being able to hand feed them once they have become accustomed to you, they are such a tame fish that they will even allow you to stroke and pet them. Always take care if feeding this way, remember the section about the sting in the tail :-):
It is best to feed the fish blood worms or tubifex worms when they are first added to the tank, you need to get them feeding as quickly as possible. When purchasing your ray, check with the supplier that it is acclimatised and already feeding, if not you may have problems getting it to eat at all. Once the ray is eating you can vary the diet by offering prawns, chopped earth worms, brine shrimp, mussels and cockles. Most specimens should also accept commercial foods with a little patience.

Breeding Freshwater Stingrays
Stingrays are live bearers, they are classed as ovoviviparous. This simply means that they produce eggs but they do not have a placenta or umbilicus. They produce "pups", either one is produced at each birth or it can be a multiple birth.Internally the pup is encased in a viscous egg casing which contains the yolk sac. Once the yolk sac has been consumed by the pup, it will hatch from the egg casing inside the mother and she will give birth. As soon as the pups are born they possess a full set of dental plates and are quite capable of caring for themselves. The mother will leave them to their own devices and in many cases will begin mating after a shoer period of time to start the cycle all over again.
The rays are easy to sex, the males will possess claspers which are located on either side of the tail (with juveniles the claspers are only seen from the underside) and these are used for grasping the female during the mating process. The females should always have a larger disc diameter then the males, if this is not the case the males can inflict serious damage to the female. Fertilisation takes place internally and the gestation period should be around 3 months.
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Re: Freshwater Stingrays and how to care for them

Postby malakye » Wed Dec 09, 2009 1:24 pm

Excellent write up there Mick with some great information as always.
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Re: Freshwater Stingrays and how to care for them

Postby Graeme » Wed Dec 09, 2009 10:13 pm

That's a very interesting article Mick. The Stingray certainly is a fascinating fish.
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Re: Freshwater Stingrays and how to care for them

Postby Anita » Wed Dec 09, 2009 11:15 pm

Good profile Mick - respect :thu:
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