I wonder about this from a biological standpoint. In soil systems root exudates/metabolites drive bacterial and fungal proliferation and ultimately provide nutrient acquisition for the plant (This is where ~all trace minerals come from!). If you wanted to further naturalize your system I could imagine that perennials, whose roots are active and longer lived in the system, would better mimic the terrestrial system ecology. Annuals who may only spend several weeks in a system don't have as much time to build bacterial and/or fungal associations within their root zones. I think keeping water DO as high as possible is real important when trying to build a system ecology. ACT is recommended made at a minimum of 8ppm DO so this seems appropriate for a baseline. This means significant oxygenation is necessary for these bacterial and fungal populations to survive. We use a vertical plastic matrix which has a very high evacuation rate. I think it probably helps to have this feature because gaseous oxygen is spatially very close to roots. Still, there are better medias I can imagine.

Perennials also tend to be better able to utilize ammonium and depending on your pH and system efficiency you may have some of this that the plants could use directly. This may allow you to increase stocking density to some degree(?).

Mint does really well and is able to put on tons of biomass in short order. More aquatic species of perennials like mint are a logical bet in my mind.

-m

I think with a bit of maintenance, things like mint and cherry tomatoes work. I haven't tried mint, but I've got way to many cherry tomatoes growing, and I just need to pull out the roots every few weeks from the stand pipe. Doesn't seem to need much more than that. And with the siphon, channeling isn't a problem.