It is no secret that keeping freshwater stingrays in the home aquarium is a considerable challenge and may be frustrating for some. They are not the easiest fish to keep, but this doesn’t mean you can’t be successful in keeping them.

If you think your skill level as a fish hobbyist is that of a novice, or if you feel you cannot fully attend to your tank, then stingrays may not be the best fish for you at this point. However, if you are equipped with basic skills in successfully keeping freshwater fish and think you are ready to level up in the hobby, then I guarantee stingrays will provide you with excitement and happiness. Stingrays are not the same as your ordinary aquarium fish. They will require you to be more observant of the finer details of fishkeeping to successfully keep them. Their needs are more demanding than those of the ordinary fish you have kept. However, if you are sensitive to their needs, keeping them should be easy, and in time, (if you have a male and female pair), you will be rewarded with pups even when you don’t expect them.

Hard Versus Soft Water

If your water supply is not soft (and therefore not ideal for stingrays), the only way to remedy this is to dilute the dissolved mineral content of the water by adding “mineral-free” pure water. This will naturally make your water softer. “Mineral-free” pure water is available nowadays as bottled filtered water. To use the term “mineral water” may just result in confusion in the Philippine context. Locally, we erroneously use the term “mineral water” when we mean bottled water or water that has been processed, bottled, and sold for human consumption. Thus I used the term “mineral-free” pure water to refer to what you should use to dilute your tap water. Some brands of “mineral water” on the market are indeed true mineral water with a high amount of minerals. But if you use this, you will only increase water hardness. “Mineral-free” pure water has undergone reverse osmosis or distillation, and may be used to soften your aquarium water.

The Most Important Water Requirements

As with any other aquarium fish, the most important element to consider is your tank water. If you keep the water in your tank at optimum conditions, then you should not encounter any problems in keeping stingrays; in fact, it is your biggest responsibility. As with any fish kept in the confines of an aquarium or pond, its wellbeing will be highly reliant on the water conditions you provide. A fish lives in water, and water to a fish is everything. If the water is good, it will survive. If the water is bad, it will die. To achieve this, you have to control two variables: water parameters and water quality. These are two different things that you need control to ensure that your tank water is fit for fishes to live in.The term ‘water parameters’ refers to the composition of the water in your tank.

The science we learned in grade school has taught us that water is made up of two parts hydrogen and one part oxygen; hence H2O is what makes up water…water molecules, that is. But scoop out a glass of water from your tank, then you not only get H2O, but also a host of other elements mixed with water. Fish do not live in pure water, but in a water mixture; in other words it’s H2O plus a host of other elements, and these elements that are mixed with your water can affect your fish.

Water Parameters

1. pH: One of the most important elements in water is hydrogen. More specifically, the amount of hydrogen ions in the water mixture affect how acidic or alkaline the water is. This is what we fish hobbyists call water pH. We are familiar with this because we see this all the time when we read about caring for fish. Our fish come from different parts of the world with different water parameters; thus, it is important that fishkeepers know what pH value is best for their fish.

Research should be able to give you the pH value that best suits a species of fish. Most research materials will give a range of pH values which is comfortable for your fish to live in. Freshwater stingrays do well in slightly acidic water with a pH range between 6.0 to 6.75.

Freshwater stingrays of the genus Potamotrygon are from the Amazon river in South America. This river traverses one of the biggest rainforests in the world and is full of tree trunks, branches, and leaves, which give off tannic acid when soaked in water. Thus, the water in this river system is naturally acidic.

To keep freshwater rays in your aquarium or pond, you must maintain the pH between 6.0 to 6.75. This can be easier said than done, depending on where you live. If you live in an area where the water supply gives a pH of neutral or 7.0, then achieving the desired 6.0 to 6.75 is easy. If the water supply in your area is about pH 8.0, then bringing the values lower will be more difficult.

2. Hardness: This refers to the dissolved mineral salts and total dissolved solids in water. There are two basic types of hardness of importance to aquarists: general hardness (GH) and carbonate hardness (KH).Carbonate hardness is important to hobbyists as this refers to the buffering capacity to prevent pH from fluctuating. General hardness is basically determined by the amount of calcium and magnesium minerals in the water. This may have a direct bearing on the health of a fish. If the water hardness of the tank is ideal for the fish, then it can be reasonably expected that they will live long in that environment.

If the water hardness is wrong, then the living conditions for the fish will be so stressful that it will slowly get sick and die. Freshwater stingrays prefer soft water. This means its water must have only small amounts of calcium and magnesium. Soft water is rated at 4-8 dGH or 70-140 parts per million (ppm). 3. Temperature: Freshwater stingrays come from tropical countries just like the Philippines, so they are accustomed to warm weather. Generally, the water temperature in our tanks is fine with stingrays. It is only on a few occasions that it will be a concern. Actually, most of the time, it is the lower values that are a concern for Filipino fishkeepers, and these occur during the rainy (usually June to August) and cold (between November and February) seasons. The rest of the year, you can actually shut off your heater.

An aquarium heater with a thermostatic control should do the trick. Stingrays are best kept in water temperatures of 24-28°C. To prevent water temperatures from dipping below the 24°C level, I suggest you set your heater at 25 or 26°C. The upper temperature is not much a concern; they can tolerate up to 33°C. Anything higher should be a concern. By the way, it is best to invest in a heater guard because some rays have been burnt by the heating element of the aquarium heater. With a heater guard, the stingray will not be in contact with the heating element.

The importance of pH Manipulating the pH value of your water is very important when keeping stingrays, especially when the pH from your water supply is not within the desired pH range. This is when the fishkeeper’s experience becomes a factor. There are a few tricks up the sleeves of experienced fish hobbyists for increasing or decreasing pH levels. The safest way is to buy products for increasing or decreasing pH. These were made for the aquarium so they must work and be accurate and effective. Just follow instructions as directed and monitor the results. There are many natural ways to lower pH.

The most common way is by soaking dried leaves in the water, just as how it occurs in nature. Internet research reveals the use of dried Indian almond leaves (as these are referred to by Western fish hobbyists) is an effective way of lowering pH. Our fellow Asians refer to these as ‘ketapang’ leaves. For a while, Filipino fishkeepers had no idea what these leaves were until it was discovered that the Indian almond or ketapang tree was native to the Philippines and in fact is a very common tree we know as the Talisay (Terminalia catappa) tree. Talisay leaves are long and broad, and the branches of the tree spread wide. This tree is so common in the country you can see them just about everywhere.

In other countries, fish hobbyists pay a fortune to get their hands on dried Indian almond leaves, while we Pinoys merely sweep them off our streets and gardens and load them onto garbage trucks. To lower the pH of your water, find a talisay tree in your neighborhood. Pick up the really dried, brown-colored leaves. Rinse these well in running water to remove the dirt and put them in a net bag to soak in your tank. After some time, the tannic acid will leach out from the leaves and you will notice the water will have a slight tint. Measure your water with a tester. If the pH is within the desired range, then you may remove the leaves. If the pH is still high, keep the leaves soaking in the water longer. If your problem is that your water is too acidic and you need to increase pH, the aquarium industry also has products to increase alkalinity. Again, simply increase the alkalinity as directed and measure with a pH test kit.

A simple home remedy for temporarily increasing the pH of water is with the use of baking soda or sodium bicarbonate. This, however, is not stable enough in the long term. A big concern with adjusting water pH levels is that there may be a tendency for it to fluctuate since these are not the natural values of that particular water source. Once the desired pH is attained, you have to increase carbonate hardness to increase buffering capability, thereby keeping pH at the same levels. To do so, get crushed corals, limestone chips, or oyster shells. Rinse to remove dirt, put in a mesh bag, and use as a chemical filtration media in the sump or filter system. These will release carbonate and bicarbonate ions which will increase the carbonate hardness of the water. The presence of carbonate and bicarbonate ions will keep pH levels steady.

Water Quality

This refers to the state of cleanliness or dirtiness of your tank water. The aquarium or pond is such a limited space that your fish in its everyday existence will contribute to making the water dirty. All the organic waste given off by the fish—whether it is their feces, urine, or slime—will rot in your tank and will contribute to making the water quality poor. To ensure you have good, clean water in your tank, you must have a good filtration system and an effective maintenance program.

The harmony of these two processes will result in good water quality. There are many types of aquarium filters in the hobby, and each one should work well. But what will work the best is something you have to decide for yourself. My recommendation is for you to use a filter system rather than just a filter. A filter system is one that has three major components of filtration: mechanical, biological, and chemical filtration.

The Three Components of a Good Filter System

1. Mechanical filtration

This is the first stage in the filtration process, designed to trap solid waste matter which will then be removed from the aquarium system. The key to such a filter is to efficiently process the water and collect the debris. After collection, a mechanical filter should be cleaned periodically—say, every 4 to 7 days—to make sure the trapped organic matter will not rot in the tank. Once these are removed, the next stage filter will not have to process solid waste matter anymore and will have a smaller bio-load to process.

2. Biological filtration

This is the most important section of the filtration system because it is at this stage that organic waste matter is broken down into less toxic substances. It uses a living colony of beneficial bacteria to consume the rotting organic matter. For beneficial bacteria to stay alive and actively processing for the filtration system, they need three things: filter material to live in, oxygen for the assimilation process, and organic matter to process. Beneficial bacteria are also called aerobic bacteria because they need oxygen to breathe and live. Oxygen is present in the water as dissolved oxygen; therefore, it is safe to assume that so long as the pump in your filter is working, it is definitely supplying oxygen to the beneficial bacteria that live in the filter materials. To increase the biological activity of beneficial bacteria, they must be supplied with more oxygen.

The more oxygenated the water, the better. There are many ways to attain this: increase water surface agitation in the tank so that the water is better oxygenated, or add pumps, aerators, and the like. Increasing the oxygen supply to the beneficial bacteria improves their processing capability for breaking down organic matter into ammonia, then into nitrites, and further into nitrates. Lastly, beneficial bacteria need food to live, and this is the organic matter they process. So long as you have fish in the tank, then there should be a continuous supply of this. The only concern is if the tank is overpopulated to the point that your filter cannot process the bioload efficiently; in this case, you must increase the capacity of your filter.

3. Chemical filtration

This is the third component of a total filtration system. The use of a buffer media in the form of crushed corals, limestone, or oyster shells are good examples of chemical filtration for a stingray tank. This way, a good level of carbonate hardness will be maintained to keep pH levels at a desired value. Use of activated carbon is always good when building a chamber for chemical filtration. Activated carbon is particularly good in removing odors and, to some extent, chlorine.

Why the Correct Use of Filters is Crucial

The material in which the beneficial bacteria live is the filter media. Beneficial bacteria will colonize the filter media and process dirt there. There are so many kinds of biological filter media in the market, and all of them work. Some may have advantages in terms of efficiency over the others, but the bottom line is that they all work, especially if you use them correctly, for the purpose they were designed for. Let me cite the use of bioballs. These were designed for maximum aeration and are the best filter media for the dry section of the trickle filter (the dry section is the chamber where water merely trickles; the wet section is the chamber that is completely submerged in water).

If bioballs are used in the dry section of the trickle filter, then they are at their maximum efficiency. If the same bioballs were stuffed in a canister filter; they may still work but very poorly and inefficiently. On the other hand, bacteria house, bakki rolls, ceramic rings, and a host of other filter media are designed to be submerged in water, so they work best when used for wet sections. If used in the dry sections of the trickle filter, they will still work, but not efficiently. If you look at fish hobbyists today, I would say about 80% of trickle filter users are guilty of this mistake. Just because these expensive high-end filter media are popular doesn’t mean they are always effective, especially if used the wrong way. Your old school bioballs were designed for the dry section and until now their efficiency when used correctly is yet to be matched. The key therefore is using the correct filter media for the correct purpose to maximize efficiency.

The Importance of Good Maintenance

Next to having a good and efficient filter system is having an effective maintenance program. An effective maintenance program involves how one maintains the water, the filter system, and the aquarium itself. Water in the aquarium deteriorates because fish excrete waste matter. Yes, you may have an efficient filter that converts these organic wastes into ammonia, then nitrites, and eventually, nitrates. However, in time, nitrates will accumulate and eventually poison the fish if you don’t intervene to maintain the quality of your water.The solution for this is to change the water periodically. This dilutes the amount of nitrates in the aquarium and keeps them at low and safe levels.

For freshwater rays, a 20% water change weekly should be a good habit to practice. This ensures that your nitrate levels are always in check. The filter system is another section that needs to be maintained regularly, but over a longer period of time. If your filtration system is of adequate capacity, then you only need to clean this maybe once every quarter. Simply rinse the filter materials with water coming from the tank.

Your objective is to remove debris stuck in the media. You should not aim for a 100% cleaning, to the point that your media is devoid of dirt and bacteria. You simply want to remove gunk so that water can flow more freely. Remember that if you keep the filter media somewhat ‘dirty’, the beneficial bacteria living in it still have enough organic matter to eat. Once you turn on the pump, they will continue to flourish and do what they do best: to process your tank efficiently. The last concern with regards to maintenance is the tank itself. This is merely an aesthetic thing that can be done when the need arises. If you have to scrape the glass because there is algae, then do so.

If there is an excessive amount of poop, then siphon them off. If the lighting needs fixing, then attend to this at your leisure. You need not do anything intense, but keeping the tank in good working order nevertheless should be part of your maintenance program. In summary, so that your stingrays will have good water, make sure you have an efficient filter and an effective maintenance program.

Remember that in keeping stingrays successfully, you must maintain good water parameters that they like. Stay within the ranges that best suit them and avoid extremes. Stingrays do not take high levels of ammonia, nitrites, and nitrates very well, so make sure you pay special attention to the quality of your water. If you provide optimum water conditions, then your stingrays will be very healthy.


To ensure that your rays are healthy, make sure they are fed well. Smaller rays may be hard to feed, especially the newborns. It is a practice among stingray breeders to feed live tubifex worms as their first food. Of course, since the tubifex are gathered from highly organic environments known to be dirty, it is a must that the tubifex you purchase be thoroughly cleaned first before being offered to the stingrays.

Rinse them in running water until the clutch is dirt-free. Once the rays have grown about 5 to 6 inches in body diameter, then the rays may be weaned off live tubifex and trained to eat fresh shrimp or strips of fresh fish. Cut these to bite sizes and offer it to them once or twice a day. Stingrays in general will eat all kinds of meaty food that fall to the bottom of the tank. Large rays can be aggressive and greedy come feeding time, so you must make sure a lot of food is offered for everyone in the tank. Bear in mind that heavy feeding will require more cleaning. This is when periodic water changes help. But don’t limit your water change to your projected schedule; if you feel you have to do an additional water change because of the heavy bioload, go ahead and do off-schedule partial water change. Stay within 20% and everything should be fine.

The Tank

Stingrays are huge fish and therefore will require a big tank. While most are sold as 5-inch cuties, these will grow to huge monsters with disc diameters of well over 20 inches. A tank measuring 48 inches by 24 inches with a height of 18 inches should be the minimum tank size for an adult stingray. Having two in such a tank may be pushing it. The bigger the tank, the better it is for the rays. After all, it is true that larger tanks have more stable conditions.

A question that is often asked is if it advisable to put sand in a stingray tank. The answer really depends on the fish hobbyist. It is true that a bare tank will be much easier to clean. The dirt will be easy to siphon off, and keeping water in optimum conditions will be much easier. Having sand, though, is nicer, as this will enable the fishkeeper to observe the natural ray behavior of burying itself in the sand with only the eyes peering out.

This is like having your own NatGeo channel in your home. There will be tradeoffs insofar as tank cleanliness is concerned, and cleaning the sand will be another concern. To do this, you have to use a gravel cleaner to ensure that debris is removed from the sand when you do a water change.An important point to remember if you opt to put in a substrate is to choose sand with small, fine grains and no sharp edges. Since stingrays naturally bury themselves in the substrate, there is the risk of injury if the grains of the sand are sharp.

Therefore, choose the substrate wisely. A thickness of 1½ to 2 inches of sand should be good in a tank. Any thinner may result in bare spots which the stingrays may uncover by moving about in the tank. Lastly—although the probability is very low, almost nil—use a tank cover to prevent the stingray from jumping out of the tank. Stingrays generally do not jump out, but you do not want to regret it in case the ray accidentally escapes. An alternative to this is to provide a clearance of at least 8 inches between the top of the tank and the water surface. This should be an ample distance to prevent the ray from flipping over the edge.


Lastly, keeping rays requires utmost attention paid to safety concerns. Stingrays are not as docile as, say, goldfish, and can be quite dangerous because of their venomous stingers—after all, these gave them their names. The stinger located halfway along the tail is a bone packed with venom. This is very brittle and will break immediately when impaled in something. The stinger has tiny barbs facing the opposite direction. So once it is impaled in something, it will be very difficult to pull out because the barbs will latch on to the flesh while venom is being injected.

The potency and kind of venom depends on the species, and some are more toxic than others. But one thing is for certain; the sting is very painful, and no fish hobbyist deserves to experience this. The key to safety is giving the stingray the respect it deserves. The stinger is a defensive weapon and the stingray will not use it unless provoked. Always give the ray a space in which it will not feel threatened. Better yet, keep hands out of the tank at all times, if possible.

If you have to put your hands in the tank, make sure the stingray is on the other side of the tank when you are working on your side. If the ray approaches your side, pull out your hands and wait until it is out of your area, or work on the area it just came from. Keep safety rules simple: stay away from your ray! Should the worst happen and you get stung by a ray, experts suggest that you soak the affected area in hot water or cover it with a towel soaked in hot water.

This is said to minimize the pain; once settled, the victim must be brought to the hospital quickly. Stingray keeping may be challenging as compared to most aquarium fish. Husbandry is nothing different, except that it is more thorough to ensure the best water conditions are offered, and that one is mindful of one’s safety. These things are the same things we do when keeping other fish; we just need to be more careful to avoid any ill consequences. A stingray, after all, is a freshwater fish, just like any another fish we fishkeepers would love to see in our tanks!

This appeared in Animal Scene’s August 2015 issue.