My short experience with a F/W stingray
by Francesco Zezza
Foreword: The title says it all. People who know me well are aware of how much I’ve been waiting for this hard to keep fish to meet the challenge of taking care of my first "non-bony" fish. Regrettably, I have to report the untimely and unexpected death of my ray, which died for no apparent reason! Among ray keepers (I’m member of a discussion group – something like EAC – on the matter) this fact, even if not that common, is known and referred to as "sudden ray death". It has happened to other more experienced ray keepers who, after long chats and studies, encouraged me to give F/W water sting rays a try … but this, all in all, doesn’t heal my (deep) sorrow that much.
The ray, being a juvenile and unsexed, was nicknamed Valentine-X (where "X" shows the unknown gender) having been purchased (as a reciprocate gift) on Valentine’s Day!
Enough with sorrow. Now, anyway, here comes what I’ve learned.
A Few words on origin, evolution, and original biotopes: Freshwater stingrays, as odd as it may seem, are much closer – from an evolutional point of view - to Pacific rays than to their counterparts living in the Atlantic. Ages ago they got trapped while browsing for food in an estuarine area in what is the actual Amazon basin when the Andes rose (because of a terrific earthquake). Before that time, the Amazon river was flowing, as a matter of fact, into the Pacific ocean. As a consequence of that traumatic (at least from a geological point of view) event, the salt rate begun to lower, and step by step, the Amazon rays became used to fresh water. At the present time, other rays from Africa and the Far East can be considered, from a biological point of view, the link between Amazonian FW stingrays and the ones living in salt environments. About 90% of FW stingrays presently available for the hobbyist’s market are from the Amazon Basin.
Aquarium keeping (aquascaping, specific needs, tank mates). Rays to be kept in aquarium should be chosen from already quarantined (and YET feeding) specimens. Dealing with newly arrived wild collected specimens may result in being a tricky matter. Never forget that rays are scaleless fishes, and treating them properly is neither easy nor "simple". Under given circumstances, rays have to get an antibiotic (or other drug) by injection (simply think about drug’s quantity to inject!). The second point to consider when it comes to dealing with rays is THINK BIG, as big as you can … and then go a step further! Some specimens such as "Otorongo Ray" are reported to attain up to one meter in disc size. Growth rate is related to food supply, to a certain degree, but correctly kept rays are said to be fierce feeders and fast growers! When dealing with small/medium sized rays aquascaping in the tank could be in the "Amazon River" fashion but, then, when it comes to dealing with adult (and possibly large) specimens, their size and strength has to be, as a matter of fact, taken into due consideration! Tank mates have to be, then, chosen (beyond other rays) among Amazon heavyweights such as Oscar (Astronotus ocellatus), Arowana, and more; even if there are reports of rays happily going on with Discus and Angels (P. scalare/P. altum) and even "big sized" characins in their quarters! Housing sucker mouth catfishes with rays can be a risky matter, despite the fact they come from the same biotope, since most of the former fishes (catfish) have, or could have, the bad habit of "sucking" the slime coat from the ray and this habit could result, in the end, in bleeding wounds likely to end as infection "start-center". BTW, most feared are said to be "common plecos" (hypostomus sp.). I’m aware of a good compatibility between rays of different kinds, even with a fair difference in size, and aggressiveness is almost always at low levels! One of the habits shown by rays to declare their own higher lever in tank’s hierarchy (against other conspecifics) is known as " topping": the dominant specimens simply tops (swim over him and the rest) another one: A bit far from cichlid’s habits, isn’t it?
Aquarium keeping (Technical supply, water chemistry, feeding). When dealing with those fishes filters (always use more than one unit: better safe than sorry!), they are always, no matter how hard you try, undersized. When aquascaping the tank, special care should to be put in place to avoid contact between rays and heater(s) unit especially if of high power (in terms of applied watts): FW ray get burnt EASILY! And their recovery is said to be anything but easy! These wonderful creatures are extremely sensitive to high (well below cichlids average, FYI!) levels of nitrite/nitrates. Warning: when readings go beyond certain limits over extended periods – no sure level is reported – this may result in a sort of irreversible poisoning ending with the death of the animal. Hence, frequent water changes are a must, with suggestions ranging from 20% every two weeks up to 30/50% (and more!) weekly, depending on the ray(s) size, tank size, and filters in use. Water chemistry should be kept on the acidic/neutral side, with water temperature neither below 22° C, nor exceeding 30° C. Whenever something goes wrong with water chemistry, FW rays show their dislike by stopping to get food and/or showing a lethargic behaviour. Feed them with HEALTHY feeder fishes (this could trigger them to start chasing smaller tank mates; be conservative!), fish’s fillets, shrimps/prawn, earthworms, mealworms, and alike. They should refuse, as a rule, "canned" food.
Aquarium keeping (Rays requiring special cares): Rays such as the one commonly known as "Antenna Ray" because of their extremely long, and at the same extent, fragile, tail DO need special dedicated tanks, and should be elected for a solo tank, unless looking for possible husbandry, allowing them to move freely and gently. Same story, but for a completely a different reason, is with rays such the "Otorongo Ray" reaching up to one meter (3 feet) in disc size once fully grown up!
Keeping rays in the aquarium: handling VENOMOUS (Kind of risk: venomous stinger) animals. Rays ARE venomous (either marine or f/w), or better yet, the stinger hidden in their tail is venomous. Beyond the fact that the f/w ray’s venom, like almost all animals living in water, is of protein origin, there’s very little known (or at least on what ALL scientists agree!). Fatalities are extremely rare, mostly occurring in the wild, (i.e.: kids playing in shallow water and/or fishermen removing ray from their nets, and mostly refer to injuries to abdomen or "big" veins), but even though the risks are low You can’t avoid considering them. As far as science knows (or BETTER, as far as I know), real risk comes from "residual of organic matter" remaining in the wound (i.e. stinger’s parts, the stinger breaks in pieces when the ray hits). Wound are – it’s said - EXTREMELY painful, and require a very long time to heal. One of the books mentioned in bibliography reports the wounded part was numb SIX YEARS after the "shot"!!!
TIP: When setting up a tank, you’re highly advised to use all technical stuff by working OUTSIDE the tank (such as canister filters), and to avoid putting your hands in the tank as much as possible .
BEWARE: Stinger are changed, by an healthy animals, every few months and are said (if untreated) to retain their venomous capacity for a LONG LONG period when buried and lost in the sand.
Further info on ray’s venom and related matters can be found here
In the case of injuries (like all organic venoms), first aid is dipping the wound in hot (as hot as you can stand!) water and IMMEDIATELY after look for medical survey. This is a matter to be seriously handled! A real "drug" against F/W venom does NOT exist! Doctors will survey the situation to avoid infections and/or related sign/symptoms/complications. CLEARLY tell your doctor what’s happened and expect him to consider you … … … well, let’s say the truth: MAD!
These are not fishes for a beginner or to play/kid with!!!
Husbandry and Breeding: These fishes are elasmobranches ("non-bony fishes") like sharks, marine rays, mantas and show an EXTREMELY clear sexual dimorphism, in which the mature males carry two claspers (along both sides of the tail). Reports of newborns are, mostly, related to wild females caught when already pregnant. On the other hand, almost all the captive births, as far as I know, refer to Potamotrygon motoro. Pregnancy is internal and it’s reported to last three months, and the youngsters are released (1 to 4) live and fully developed; equals in all way but size to the parents. Most ray enthusiasts keep their rays (of different species) in the same tank. I’m not aware of report of hybridization even though, to me, and also according to more experienced ray keepers, it could likely happen between rays of the same genus (but different species), like those belonging to the Potamotrygon Genus (which, by the way, is the most commonly kept). I happen to have a juvenile (likely male) Potamotrygon leopoldi.
MY OWN SHORT EXPERIENCE, IN DETAIL:
Enough with theory, let’s go for real now! Despite the fact it’s always said that You ought to begin with beginner fishes, this, at least when dealing with rays, is not that true … or better, you’re likely to begin with the ray(s) found on sale. These fishes are not that easy to find on the market. As a matter of fact, I got my ray from a wholesaler (who asked me to remain unmentioned) as a sort of personal favour (fyi: I paid for it!).
My ray is a Potamotrygon leopoldi (to my best knowledge) and, along with Potamotrygon henlei is member of the so called "Black Ray" group. Both are said to be among rays labeled as "easy" to keep. They show a dark coloured overall disc with lot of ocelli (pale in colour, refer to pics for further details). Furthermore, in Potamotrygon henlei the ocelli are present on the underside of the disc. These fishes are said to be aggressive feeders even though it was an effort to switch my ray from live (chopped and bleeding) earthworms to filleted fish and/or shrimps (but I did it). There are reports of captive P. leopoldi husbandry. These rays are said to attain a full size (disc diameter) of 45 cm (18 inches) at sexual maturity.
I keep my ray - at the moment - in my 360 lt (97 US gals) Amazon tank with all of the fishes caught in Peru two years ago (even if it could be, from a fish’s point of view, a bit scary for say … a Corydoras). The tank is serviced by two filters (running separately): a canister unit, plus a fluidized bed filter (except for a nitrate spike, despite the tank was running for over a year!). A few days after ray’s arrival, and things are, up to now, running cool …it is likely the filters had some trouble in handling a sudden and extremely high, additional bio-load. A heavy extra water change handled the matter marvelously. Never forget this old medicine! All of the technical supply servicing the tank allow an environment like this:
I do not use R.O. water but, instead, a lot of black water extract, bogwood and a self-made "oak’s leaves extract" to buffer the water to values more suitable to ray’s need. Maybe I’ll become more fussy when, if and ever, trying to breed them.
My aim is/was a tank of likely 700/800 liters (round 200/230 US gals) to house a few selected Amazon heavyweights beyond my actual ray, such as: An Arowana, another ray (trying to get a breeding pair) and a, just an idea at the moment, Sorubim lima (aka Lima Shovelnose) or two Oscars (Astronotus Ocellatus). This tank, moderately aquascaped (an Aro needs a lot of room to swim; a ray a lot of room to rest), serviced by a slightly subdued light, filled with brownish water (resembling the Amazon’s black waters), and serviced by the very best of technology I can afford should be quite a masterpiece to look at, don’t you think?
BOOKS ON THE MATTER
You can find more about those two books here.
And here are some pics of my ray:
First things first:
How the ray arrived home (from the wholesaler’s warehouse). Anyone who has been involved in moving fishes should recognize it at once!
How the fish – below - looked immediately after having opened the box and the plastic bag. All in all, in quite good shape. The fish has been quarantined by the importer and I had to trust him and introduce the ray in the main tank immediately: No room to quarantine him elsewhere. Who dares wins … (but only God knows how hard I tried to avoid this risk!)
And here comes – above - a closer look: The colour pattern clearly identifies him (it is a supposed male) as a member of the "Black Ray" group. The dreadful stinger is in sight along the right edge of the tail. Never forget it when looking at your new cool, tame, friendly pet …
And now, at last, the ray in the tank, These pics – following - were shot a few days after the arrival, when the ray was finally used to his new environment and had begun to investigate the whole tank to get how things are running (and looking for a morsel of food, of course!)
Under the bogwood along the rear wall of the tank (seen in detail on the upper edge of the pic), it’s easy to find some food that wasn't spotted during dinner time. The ray (also nicknamed "Bulldozer" or "Caterpillar" because of his unbelievable ability to dig and bury himself in the sand!!!) immediately got the message. A close look all along the edge is now a must whenever he undergoes a check of the tank …
Isn’t he lovely? Dunno if I needed to reckon this song or not, but, all the same, I like my ray a lot … I’m so happy Stefania decided this would have been our reciprocated (we paid half each for him) Valentine’s gift. Isn't way better of a scarf or a tie?!?!?!?
THE TANK: AN OVERALL VIEW …
And now to end with two pics of the tank where the ray is housed. Don’t trust them …A ray IS a messy fish …
1st pic: General view of the tank. A bit dark but subdued light help Amazon fish to thrive.
2nd pic: A bit closer (a Pterophyllum sp. "Peru" – an Angel, from Peru in in sight at right corner). Due to my laziness the front glass isn’t that clean (Shame on you, Francesco!) and the pic is a bit messy!
A short video clip showing my Potamotrygon leopoldi
Many thanks to Carli De Busk for her editorial help.