While not ideal 20" is enough depth for rays to breed. One of my ray tanks is 9.5'X4'and only 13" tall and 3 different pairs that size and bigger have breed in it.
i have been going back and forth on that idea..
But i think i found the tank i am looking for..
its at Plastic-mart.com
its a spill container...its white but i am going to paint the bottom black with krylon fusion paint.
its pretty much exactly what i want..i would just like it to be 30" tall instead of 24"..
Krylon comes off real easy. Siphoning will probably leave little lines. Once it's scratched it might peel. Don't want rays growing up on paint chips.... lol.
If you wanted to take it to the next level you could use a liner and concave the bottom with a drain. Few korilias to spin the entire thing and cracking a valve on that drain is gonna get rid of any uneaten food or solid waste before it even hits any filters or gets broke up ending up in the pads/socks.
If you build with bolts you could take apart through doors and reassemble. It would be easier to move. My vote is liner all the way, a blue one. Any kind of liner/tub/tank is going to be limited to where you can get it. A liner won't. Give them a half foot deep basking area with halides on one end and a deep dark part where they can hide....... Not to mention a framed liner type pond has to be a lot cheaper. You could even get all fancy and hide all the plumming in it. Might have been tank 125 that built a real nice pond hiding lines in the walls of the pond.
those are great idea's and i hate to sound like a lazy ass...but thats too much work!
for now anyway...
maybe though..i wont make any decisions for a couple weeks.