Second account is full up again

My Google account is bursting with pictures.

So clever me quickly opened another, empty account which I connected to the Google Photos app on my smartphone.

What I hadn't anticipated however is that all the old pictures were uploaded from my smartphone, so the new account was quickly overflowing again. And now I had plenty of redundant pictures.

So how do I avoid this situation with a "fresh" Google account, i. e. a newly opened one, or one where all the pictures have been deleted?

Thank you.