Hi,

I didn't quite get it from your question. If you want to get rid of the old generation of plants and get a new one growing, I would drain everything out and start with a new solution. But, if I were in the middle of the growing cycle, I wouldn't empty anything out. I would just run the water trough a filter and keep an eye on algae, diseases, nutrient levels, etc.

Hope that helps

Hitech Farmer