After harvesting 2/3 of phyto culture, how do you rebuild it?

[CIMulation]

I'm trying to understand how to grow phyto to feed to rotifers, but I'm having trouble understanding the part of harvesting 2/3 of the phyto culture part. When you harvest 2/3 of the culture, what is the next step? Do you just add more saltwater and they'll reproduce on their own or what? TIA

 

[Kathy55g]

I store bleached saltwater (1 ml bleach per gallon 20-25 ppt saltwater) up to the two thirds full mark on 2 liter pop bottles. At harvest time, I dechlorinate a bottle, add fertilizer and pour the ripe phyto into the dechlorinated bottle up to the top-2 inches. Add air and light and come back in a week to do it again.

The bleach effectively sterilizes the bottle and the water at the same time. Always propagate the phyto before you touch the rots. Avoids contamination.