Legal to use water from a goldfish tank?

[terrydavis]

If I do not change the goldfish food, water temperature, or the way I change the water, location of the tank, etc. ....Can I use the "old" water without a form 5A or a Qualified Scientist?

[SFsciguy1994]

Hello!

In order to be ethical, it would depend on the length of time you wouldn't change the food or water. Would you please be able to give a few more details about what you plan to do, and how long you want to do it for?

Thanks