I am very interested in this project! I ran some experiments for a warm water 681 liter (180 gallon) NPS tank. I had no problem growing rotifers in tall tubes. I used a 6" inch diameter, 6 foot tall highly aerated tube that circulates 8 liters (2 or 3 gallons) per day, to and from the display tank. I fed it phyto paste. I have built a robot to feed six of these towers that are stacked along the wall in the garage with heaters in them.
As a side note, I also had no problems growing artemia in a 208 liter (55 gallon) closed system tank using filter feeder powdered food. All this of course is at a room temp environment.
I have been afraid of trying phytoplankton. The small bottles, constant cleaning and frequent crashes has made me avoid it for decades.
The longer term life between crashes, in a recirculating system sounds intriguing. Whether I can apply any of this process is a big question.
I have some 208 liter (55G) tanks and a 492 liter (130G) tank that I could use. Or maybe I could enlist some more towers. I also am building a Ca reactor that will be feeding about 30 to 50 milliliters per minute through it. I guess that I could use the effluent to work on phytoplankton.
I'm a designer, not a biologist so some of what is talked about goes over my head but I will tag along.