Try here:

Here is a link that might be useful: Excellent Hydro Book

This website has almost as much info as How-To-Hydroponics and its free

Here is a link that might be useful: alternative-innovation

The most useful book I have was recommended by someone here long ago. It's a textbook I think, called "Hydroponic Food Production" and was written by Dr. Howard Resh.

It's a good book. I also owe a lot to the link below for much of my early learning. I still go there to check for answers.

Here is a link that might be useful: Website resource