Relatively straightforward question: In an aquaponic system with multiple grow beds, can one bed drain into another (series), or do all beds need to flood/drain independently (parallel)?
Grow beds can drain parallel or serially but in the latter case a failure anywhere affects the whole system and not just a single bed. So, if for example you were using bell siphons, and one of the siphons stopped working, then water could potentially all dump into one grow bed and never leave.
There's also the issue of solids which accumulate inside the grow beds. You would probably find that the first grow bed in the system would accumulate all the solids if they haven't been prefiltered, and that could affect the drainage.
And finally the plants presumably get less and less nutrient as they pass through the beds so that the bed at the end of the series has the least nutrient present which may not be what you want