Something like this would work for a pond:

but they don't say much about how I cared for the Ray. Let me know and I'd be happy to post more pics and add a description of the entire setup including acclimation, care and feeding. What I did there for that Ray in the 120 will work just as well for any of the family of Carpet Sharks.

The tank size recommendations found everywhere online logically assume that the tank will have a pile of LR sitting on the bottom. That's why they don't recommend a 120 gal tank, but I found that the Ray did just fine because the entire bottom of the tank was open swimming space, over soft Utah Oolitic Sand, with plenty of cover under the suspended reef. 

Sand is very important. The deep bed of Oolitic Sand that I used there, and still today provide for local hobbyists, is perfect for these "bottom sliders" and it did an awesome job of biofiltration, so good in fact that no filtration "equipment" was needed, not even a skimmer. 

Cover is very important. All marine fishes do a lot better when they have plenty of hiding spaces.

Aloha,

Mark  

P.S.

Found this memorial to our wonderful Ms. Ray (unlike the teacher in Finding Nemo, who was also a Blue Spotted Ribbontail Ray, ours was female), which helps explain why these fish are so cool to keep as pets.

Of all the reef aquariums I've had over the years, my favorite of all time was the one where I built a suspended reef that housed a Blue Spotted Ribbontail Ray, a Batfish and some common small reef fish. It's pictured here:

That's copied from the Reefkeeping Tips, linked below in my signature line, which, if you've been here since 2009, you've probably seen and hopefully found useful. 

Because that suspended reef tank was so popular, later on I responded to requests to tell how I built it. The write up is here on the forum somewhere, if I can find it.

Aloha,

Mark  

I have many more pics of Ms. Ray and Mr. Bat and would be happy to show them off if you want to see them.