It varies some sturgeons are fast growers and some are slower growers depending on what type. They average a ft a year with the bigger species growing faster of course. And it's always different with each fish it's an individual thing some as we know some grow real slow. They can live in cold and warm water temps rather they can tolerate various temp. But cold water is whats best for sturgies. As for tank size well it's a known fact that most sturgies get 3ft plus at adulthood. Therefore you will need to provide a bigger tank/pond for the sturgeon as it gets bigger. However, that doesn't mean you can't grow the fish out in a smaller sized aquariums.
I'd also like to mention that some people are too anal. Some people need to relax and cut back on all the negativity. So here is my thought on some of the responses about animal cruelty and insufficient/inadequete housing of fishes. Well it's hypocritical to be saying something like that especially if the ones who preach it have pets themselves. Lets face it Anyone who has a pet is guilty of animal cruelty if we want to be anal about it right? After all what animal wants to be held captive or housed in a cage, house, or tank/pond and what not. We all know that these animals we so called pets would much prefer to roam the great outdoors as they wish right. We keep them as pets and they don't have a say in it because they can't talk they are animals they have no say in what we do to them for example keeping them as pets. Second no one on mfk or not on mfk will ever be able to provide a right home for the fishes we all keep. We don't own huge lakes, the ocean, nor huge rivers like the amazon or mekong. Therefore anal wise we are all guilty of animal cruelty for keeping them in smaller bodies of water compared lakes and rivers and the ocean. So just relax, of course it's not practical housing such huge growing fishes in average mfk sized tanks 100gal to your thousands of gal home aquariums for life. However, it doesn't mean you can't grow them out in your average mfk sized tanks right. After all it's not like people asking such questions are saying hey I have a 12ft sturgeon can I keep it in a 1000 gallon tank? So when someone asks a ridiculous question like that feel free to go anal, but lets try not to be to anal everytime we see a post about a large species.