Ebb & Flow questions????

I'm using a 50gal res..

1- I plan to change the res water every 7-10 days.. is this okay?

2- So I add nutes after I change the res water but do I add any during the week or just keep topping up with plain ph'd water and add nutes only once every 7-10 days when I change the res water?

If you have a TDS go by how much they are eating. If you dont then I wouldnt worry about adding nutes since you will be changing water ever week. TDS meter is the best way