Hello. A Vic pond does not have to be huge, though for the best display I'd recommend at least an 8' X 8'. I grew them in 6' wide ponds and it really cramped their style, but I was growing them to only be a shippable size and not a show plant.. As for depth....if you have ever seen Kit Knott's Victoria pictures on victoria adventure.org they were grown in 20" deep ponds, so 24" would be more than ample. One thing to consider is they may have to be stepped down. If you are growing from seed, the starts do best in relatively shallow water and can be set in deeper waters as you uppot them. If you plan to get 'plants', it has been my experience that most commercially grown Vics are cultivated in about 16" ponds, but given pot size, they may only have 8"- 10" of water over the plant and when you receive it, you do not want to plant it in such a way that the pads are submerged for more that a few hours. The petioles will stretch quite a bit, but if they pads are not floating by the next morning you will want to place it on some support to raise the plant so the pads reach the surface.
Hope this helps, don't hesitate if you have other questions.
Truth is not what you want it to be; it is what it is. And you must bend to its power or live a lie.― Miyamoto Musashi
"Knowledge speaks, but wisdom listens." ~ Jimi Hendrix
The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge.― Stephen Hawking
Craig