Phytoplankton culturing question (how to test if it's done)

[tomtom5280]

I tried culturing nanno for the first time. Over the first 6 days, it is getting a darker green. I wasn't sure if there is a way to test if it's ready besides just doing the color test? I tested for nitrates, and it's at 25ppm. Should I wait until nitrates hit zero to indicate all the f/2 has been depleted?

On a side note, out of curiosity I tested the live Phyto which I had purchased (and used as the initial starter) and was surprised to find that it tested at 100ppm. Should I be concerned that the phyto I purchased is high in nitrates? Does it mean the supplier isn't culturing it correctly (i.e. pulling it too early before it's done?).

 

[Subsea]

“Should I be concerned that the phyto I purchased is high in nitrates? Does it mean the supplier isn't culturing it correctly (i.e. pulling it too early before it's done?).“

NO & NO.

I only use the darker color test. However, if you need a number than inorganic nitrate is easily monitored and if depleted you waited too long. When I harvest, I leave 1/3 as a starter culture for the next batch which gets a fresh dose of f/2 fertilizer.

@tomtom5280 l
If I was shipping phytoplankton, I would give it extra nutrients for consumption during transit and a good start.