Ideally it would be extruded diamond, but that technology will not be available until early in the 26th century. Second would be clear aluminum, but again that will not be available for another 150 years.

Just one question: Why did you give my homie Stephen Hawking the cold shoulder when he hosted a party[0] for time travelers in 2009?

[0] https://www.atlasobscura.com/articles/stephen-hawking-time-t...

The entire problem is that acrylic is not plastic enough, so it fails catastrophically. Well, diamond has all the nice features for structure building, but it's even britter than acrylic. So your sci-fi diamond tank would fail in an even more sensational way.

We have clear aluminium already in the form of sapphire glass (Al₂O₃). Presumably you're referring to a means of manufacturing it at a scale suitable for, say, an aquarium?

It's a Star Trek joke: https://www.youtube.com/watch?v=Wv5FGCeIP8I

Acrylic is the best material for this application we currently have. If we had a better material, we would use it.

Polycarbonate is stronger and more shatter-resistant (it's used for fighter jet canopies, among other things) but also substantially more expensive.

Transparent aluminum

maybe we could focus in shape also, not only material.