What freshwater rays are suitable for keeping in an aquarium?

It appears to be a difficult proposition. Here is some information on this site. This is an excerpt:

“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?”

Crikey!

Rays are really hard to keep. Not the most hardy animal, and your going to need a very large tank. At the fish store i work at now, we currently have some rays living along with freshwater flounder and Dicus, because they both require high water quality. If you do end up getting a ray, good luck and make sure you keep an eye on it when your cleaning the tank, my friend got stung between his fingers by one. He said it was the worst pain hes ever felt, his hand was swollen for 3 weeks.

Thank you both for the information, but I have another question:

I figured a large tank was a given, but none of the information I’ve read even hints at a specific size. 50 gallons? 100? Any idea?

We have ours in a 125 but i think it could do to be a bit larger. If you dont have a tank already, get a long one as to provide the ray with more swimming area since they primarily stay on the bottom you dont need to worry about the height so much.