is it okay to put shell conditioner on aquatic turtles?

Turtle Shell Conditioner

It won't kill the turtle. That's the good news. The bad news is that it won't help the turtle either.

There haven't been any proven benefits to conditioners such as Shell Saver or VitaShell other than the cosmetic effect of making the shell look shiny. In fact, the oils in the product may actually do more harm than good by trapping in bacteria or fungus which can lead to infections or shell rot. These types of products may also interfere with the natural scute shedding process.

The best thing you can do to keep your turtles' shells strong and healthy is to provide them with a calcium-rich diet and a good UVB light. The shell conditioner, though, makes a great skin lotion for your hands!

If it's the VitaShell stuff, they're selling it to make money it does more harm on your turtle than help it. Turtles bask to dry out their shell (to prevent shell rot), putting the shell conditioner on doesn't allow the shell to breathe or properly dry out.