Thanks guys, that was the question I was asking "minimum depth to breed rays".
Didn't mean to cause any disagreements, apologies for that.
It was very interesting to know big rays can breed in as little as 12" of water, albeit not really recommended, even by oldfish who has done it.
I've been quite successful with 24" of water, was hoping to get away with 18-20" as there's a big difference in price on 30" deep (15mm glass) compared to 24" deep (12mm glass).
Please keep posting successful breeding depths as it would be great to know what others are using, plus I've got a few more months to decide .
The thing is if the tank is 12" tall you usually have a 2" gap at the top where the water line is so you only really have 9-10" of water that's not a tank it's a puddle
I think 12" tall is to shallow for adult rays to breed
If you had 2 x 18" disk rays trying to breed in a 12" tall tank I think it would be hard for the male to flip the female and you would get lots of water spillage
I think 24" tall is the bare min for adult rays
I know for sure my big rays wouldn't be happy in 12" tall