Reservoir size related to anything ?

[stuartambient]

I'm working on constructing a home hydro system, ebb and flow design.

Is there a way of determining or some kind of established rule about how the size of the reservoir and the amount of plants ? I have an 18 gallon tote now and was thinking that might be about 9, from what I've seen seems right. Wanted to throw this out though. I just don't know enough. Reading, searching. By the way I'll be starting with lettuce, progressing though as I go.

TIA
Stuart