Why Freshwater Stingrays Die: Guide to Prevention

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Stingray King
MFK Member
Jul 2, 2005
Spokane, WA
After seeing repetitive posts, and seeing that our sticky's are informational but not as in depth or organized as I would like.. I decided to take a time to give a write-up based on everything I know that causes premature deaths in FW Stingrays.

I hope this helps any new potential stingray owners make the right decisions before purchasing one of these amazing animals.

  1. Water Quality Freshwater Stingray are sensitive to water parameters.
    • Ammonia
      Ammonia is incredibly lethal to all fish. Ammonia is more toxic the higher the pH. Stingrays produce a massive amount of ammonia due to their osmoregulatory system that has evolved to sustain life in completely freshwater. They have repressed rectal glands, a tool for managing salts in osmosis, but this also means they can not retrain urea and ammonia like most Saltwater fish. These internal functions are what make FW stingrays produce more ammonia than their body could seemingly produce, even at juvenile sizes. Most freshwater fish have the ability to retain urea within the plasma of their blood, but due to a FW stingrays unique osmoregulatory system they no longer have this ability. The ability to retain urea within plasma serves as a detoxification tool for environmental ammonia, thus making Stingrays more susceptible to ammonia poisoning. This is where dilution and water volume become very important.
    • Nitrite
      Nitrite poisoning is also very lethal to all fish. Small amounts of aquarium salt will have neutralize the effects of nitrite poisoning. If you have traces of nitrites in your tank, it is a sign that you do not have enough nitrifying bacteria to handle the amount of ammonia being released into the tank. Please do thorough amounts of research on the nitrogen cycle, nitrosomas, nitrobacter, and how to properly prepare your biological media for the introduction of FW stingrays into your tank.
    • Nitrate
      Nitrate, being the end product of the nitrogen cycle, is the least harmful waste substance to freshwater aquaria. At higher concentrations however, they can irritate sensitive fish, especially FW Stingrays. Large, frequent water changes are a must when keeping stingrays, as their massive ammonia production will cause rapid increase in Nitrate. The only way to combat this is by water changes, and dilution through larger volumes of water.
    • pH
      Many people will tell you that stingrays are pH sensitive. I would have to disagree. Although many animals will obtain negative side effects longterm from being kept out of their natural pH range. Stingrays are very adaptable as they have shown by migrating into freshwater in the short span of 67 million years and modifying their entire internal osmosis process to accommodate this migration. I have seen rays kept in a pH ranging from 5.0 to 8.0. I have 'squirt and dump' acclimated wild stingrays from South American water straight into 7.8ph with no negative side effects. Some stingray species are more sensitive than others (tigers, flowers) and it helps if a slow acclimation process is in place. Try to match the pH of the water source in which you are purchasing the stingray from. Have your tank attempt to mirror water parameters, and then slowly change your pH through small frequent water changes over a few weeks to months period. It is best that your tanks pH matches that of your tap water, making large frequent water changes less stressful, and opening up the ability to do large emergency water changes of 70% or more.
  2. Shipping Shipping Methods stress Stingrays.
    • Fisherman
      The fisherman who collect the freshwater stingrays in the amazon, sometimes use methods that will endure lasting stress on your ray. Most juvenile rays I would presume are caught with large throw nets, and separated out from other fishes. I have heard that larger or specialty rays will often get caught with lines and hooks, and the hooks can cause internal damage to the mouth, gills, or stomach from being swallowed. The fisherman then transport the fish to collectors via misc. methods, such as shallow plastic tubs with no aeration and minimal water volume. Bicycle or Automobile optional.
    • Collectors
      Collectors are usually located in a variety of villages and cities, such as Iquitos or Pucallpa. They are in contact with both the exporters and the collectors. They tend to have more primitive fish facilities, with aeration and no filtration. Tanks, tubs, tile ponds, cement ponds, buckets.. all used as containers for collecting fish. Their goal is to move fish as quickly as possible, and no one tends to feed the fish the entire time to prevent ammonia. At one time many practices were very primitive, but with the internet and communications the methods being used are much better. Still, the confusion with stingray identification starts here, these people have free reign to name Rays whatever they think they are.
    • Exporters
      Exporters are usually located in larger cities with major airports, such as Lima, Peru and Manaus, Brazil. They usually house and quarantine the fish for a few weeks, and export to their customers in other countries. Depending on the quality of the exporter, they will treat, feed, and condition the fish for exportation and life in aquaria. Some treat stingrays just as any other fish, however.
    • Importers
      Importers very in size and quality, and many of them have different beliefs. The quality of most stingrays take a huge downslide at this point. They treat them as a normal aquarium fish, put them in undersized tank, fail to recognize parasite control, feed them improper foods(feeders), and expose them to poor water quality. They look at them as a fast moving profit fish, and mis-label them in whichever way will sell them best. "Teacup" Stingray is the manifestation of negligent importers not taking the time to try to ID them.
    • Local Fish Store
      This is why stingray research is so imperative, because a LFS might not know as much as they think know about them. They often look at them as a high profit trophy fish that will sell quickly. Make sure your LFS either knows what they are doing, or you know how to rescue a stingray. Ask to watch it eat first, and make sure it is eating well. Ask about parasites. If it's in an undersized tank, skinny with hips, it's probably going to die.
    • What does this mean?
      Your stingray is being shipped all over the place, being exposed to ammonia every time they are stuck in a small container. Being starved the entire time. Being put in glass boxes after being pulled out of the wild. This can all cause long lasting detrimental effects and that is why you need to make sure you purchase a healthy stingray and do your research first.
  3. Parasites Stingrays and Internal Parasites are synonymous.
    • Quarantine
      Find out if your ray was QT'ed at any point for parasites. Ask what kind of meds they used. The more you can understand about solving this problem when the rays are young or new, the easier time you will have.
    • Identification
      If your lucky, you can have someone ID your parasites. This usually requires a fecal sample through a microscope. However, any common fishkeeper can notice unhealthy fecal matter in FW Stingrays. A healthy stingray should release solid, curly, dark feces. If it is white, stringy, or broken into white particles, you likely have internal parasites.
    • Treatment
      PraziPro and Metrodazinole are the 2 chemicals I see most often recommended. However, many stingray experts strongly believe you should Identify the exact nematodes that are effecting your fish. That way you can directly treat the parasite with proven medicines, and save stress, time, and money on your QT period.
  4. Tank Size Bigger is Better, No That's too small.
    • Too Small
      75, 80, 90, 100, 110, 120, 125.. I hear these tanks being said to be 'ok' for a juvenile ray for a short period of time. I see alot of rays dying in these tanks, too? Coincidence? If you understand the amount of ammonia stingrays produce, you should also understand water volume. If you work with less water, ammonia is more concentrated, thus more lethal. Higher pH, more lethal. If you understand how often stingrays should be fed, it makes even more sense. Make sure your 'turnover' rate is much higher then you would use for regular aquarium fish. Keep in mind, if you are having problem with your 'overstocked, overfiltered, undersized' stingray tank, and your ammonia tests are coming up at 0... Your large feedings to the overstocked fish, combined with the small amount of water volume, might create a SUDDEN spike in ammonia, only to have your filtration system remove it through the biofilter within the first few hours. Thus, you check your ammonia levels later on, and immediately dismiss the thought of ammonia spikes.
    • Starting Size
      Bigger is Better, in any scenario. PLEASE, purchase the biggest tank you can get before you buy a stingray. Don't buy a stingray for your 90-125g and upgrade later, most people seldom make it that far for reasons above. It is very true that these tanks can be suitable temporary homes for stingrays, but you have to make sure you understand the needs of rays and eliminate other underlying problems before housing rays in smaller tanks. If you are novice, and want to start with less stress and more success, try to aim for 180g or larger. Height is not as much of a concern than length and width, but extra water volume is always good. 24" wide, even for juvenile rays, helps reduce stress and increase stimulation.
    • Minimum Size
      Everyone always asks the minimum size for lifetime. The smallest species will need 6x3, 8x3, or 8x4 depending on who you speak to. Either that, or a wide ponds atleast 6' in each direction. Please keep this in mind before purchasing your stingray, or have a good plan in place to find it a quality home. That means, within 3-5 years, you will need to purchase a 300-500 gallon tank for your new pet. Alot of people want to buy a stingray when they 'finally' upgrade to 125-150g tank, but don't keep in mind that there will be another upgrade right around the corner. Optimally, most common species of stingrays would do best in tanks with dimensions such as 8x4x4, 10x4, 12x4, and or a pond of 'mega-tank' of larger scale. This is reality folks, these are LARGE ANIMALS, not just fish.
  5. Feeding
    • Before you buy
      Watch it eat, know what it eats. Make sure it's been eating for a while. If it's eating but still looks skinny, it probably has parasites. If it isn't eating, and they aren't offering it blackworms yet, it will probably eat those or ghost shrimp. If it's larger, it will probably eat red wigglers, trout worms, or nightcrawlers. Inform your LFS if you have to. They seldom eat feeders and goldfish are unhealthy. Make sure you have a source of blackworms to purchase if your stingray is feeding on them. The more juvenile or 'teacup' they are, the more likely you will have to feed blackworms for some time to obtain weight and prepare for weaning.
    • After you buy
      After you purchase, feed, feed, feed. Most rays are sold as juveniles that have been starved and transported for the last 2-3 months. This is a big reason why people fail with stingrays, as they don't meet food requirements. They treat them like any other fish, but stingrays have tiny stomachs and high metabolisms. They constantly look for food in the wild and in the tank, and this expends alot of energy. Blackworms are your best starting food, and they will eat these constantly. Most people move from blackworms to smaller worms like red wigglers and trout worms, then move up to nightcrawlers. Once you get them readily eating larger worms, you can mix prepared foods such as clams, mussels, shrimp, squid, etc in with their live foods (sometimes chopped). Getting them feeding on high protein seafood will help you fulfill their calorie intake needs and get them to put on size and weight rapidly. This is when your stingray will really start to grow.
    • Why Rays love live foods
      Off-topic - But this is interesting. Freshwater Stingrays have sensory pores around the underside of their disc near their nose and mouth. These jelly-filled sensory pores, are present in most elasmobranchs and allow sharks and rays to detect minute electric fields generated by living things. This is especially useful for freshwater stingrays because it helps them to hunt down prey that might be buried in the riverbed or hiding in murky water. I have heard these also help them sense metal, thus feeding from metal feeding tongs is a good 'learning tool' to get them to eat prepared foods.

Let me know if I missed anything, or if I need to stand corrected. Most of this is my opinion, but I don't think many will disagree.


  • Tankmates
- Are any really appropriate?
Many problems present themselves when you start to find tankmates for Stingrays. Simply put, The best tankmates for stingrays are more stingrays. Stingrays immense bio-load already limits your stocking options from the start, and adding more fish will just compromise your water quality. They are very active animals that will stress out, eat, or become stressed out by tankmates.

Smaller Fish - Most small fish will become food. Stingrays are always hungry, and you would be surprised at what they will chew up even if they can not eat it. Small fish, such as tetras and other dithers, may accompany the ray for a short period, but will disappear over time. I have never heard any situations in which small fish were housed long-term with rays, except for in extra large open water displays of 1000g+ or more.

Larger Fish - Most fish large enough to not become food for Stingrays, will stress out the stingrays. Large Cichlids tend to be aggressive and territorial towards rays, and will bite the disc and eyes of the ray. A single bite from a larger fish to the eye of a stingray could prove lethal. Large catfish will out-compete for food, and compete for tank space at the bottom. Large, active, open water swimmers can stress the rays, eat food before it hits the bottom, and add extra bio-load.

What you don't see - Keep in mind that many fish have different disposition when they aren't begging for food or being put under a spot-light. Many nocturnal fish will become aggressive or hyper active at night, causing stress to the ray. Nocturnal fish often navigate and predate by sensory, and some catfish whiskers could easily confuse a stingray eyeball for a snail. Even the smallest and least conspicuous of tankmates could cause stress. So if you 'swear' your 2" skunk loach didn't kill your ray, you might want to think again.

What might work - Large, Peaceful, Placid fish. Many people have had success with a variety of tankmates, through trial and error. You will hear varied opinions, and each individual fish will have a separate disposition. Large peaceful cichlids, such as Severum, Uaru, Discus, and Geophagus have proven to be suitable tankmates. Other large open water swimming fish, such as Arowanas, Datnoids, and Silver Dollars.. Also inactive catfish, such as Tigrinus or Juruense.. Each scenario will be different, and tanksize is a huge variable.. Bioload, competition for food, adult size, growth rate, and aggression should all be taken into careful consideration before adding tankmates and jeopardizing your ray.

Still, many Stingrays Experts will tell you that they do best with no tankmates and just Stingrays. If you notice, most people who successfully raise stingrays to adulthood, and even breed them, don't have many, if any, tankmates.. Rays 'randomly' die in community tanks all the time, :screwy: ...

Acute Stress in Aquaria
- Netting, Shipping, Tankmates, Water Quality, Nutrition, Tank Space and Turning Radius can all play a factor in what they call 'acute stress.' Acute Stress is considered a small amount of stress over a long period of time, or minor stresses that are a regular occurrence. Acute Stress can suppress the immune system in fish. All of these issues that I have listed in this thread contribute to 'acute stress' in Stingrays. Many people have deemed stingrays a delicate animal, but more often than not many of these 'acute stress' factors play a major roll. The more of these stresses you eliminate, the more successful you will be.

Osmorespiratory Compromise:

1. Stress hormones released into the bloodstream cause an increase in heart-rate and an increase in blood flow to the gills.
2. The increased blood flow to the gills results in the dilation of blood vessels in the gills.
3. As the blood vessels in the gills dilate the surface area of the gills is expanded.
4. The expanded gill surface causes an increased influx of ions and water loss in saltwater fish. Conversely, freshwater fish experience an increased influx of water and loss of ions.

Adrenaline disturbs ion transport at the gill membrane, and both adrenaline and cortisol cause temporary changes in gill permeability which, in fresh water, results in dilution of the blood by excessive gain of water. Avoid handling your fish at all cost. Spooking or stressing the fish, such as tapping on the glass or playful nibbles from tankmates, will cause this surge in adrenaline.
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