[rayjay]

I culture my greenwater, rotifers and brine shrimp all at 1.017.
For hobbyists who buy the greenwater from me to add to their tanks, the amount added makes no difference in the large volume that it's added to.
For rots and brine, they should be sieved/netted from the culture water and rinsed first under the tap before being placed in the tank as food, so the s.g. they are raised in doesn't matter.
I use rots and brine shrimp of all sizes in order to feed my seahorses until they get onto frozen. I also sell to hobbyists who use the brine for many reasons. Some gut load using a specific food they want their fish to get (e.g. Selco or Algamac), some gut load a medicinal flake food that they pulverize in a blender to work on internal parasites of the fish that eat the brine, and some buy them just to watch their cats go crazy over the catnip, Uh Oh, I mean fish go crazy chasing down the live adult brine.
Adult brine grown under IDEAL conditions that I cannot duplicate, will only take 8 days to grow.
Under very low density growth, temperature of 80°, spirulina or Algama Protein Plus for feeding, very clean water, I can grow them in about 12 to 16 days.
For the density that I grow them at and just at my room temperature, it takes about 3 1/2 weeks to adult and four weeks to reproducing stage. I decapp a tablespoon of cysts and after hatchout I separate and add to 20 gallons of water, feeding greenwater for approximately 2 to 2 1/2 weeks followed by feeding with Algamac Protein Plus till grown.
In my case I have a lot of these containers for growout so that I can harvest various sizes as needed by my seahorse fry as they grow.
Personally, I no longer add greenwater to my reefs but instead add rotifers that I gut load first. I see better results that way.
For those wanting to add something but not wanting to grow rots then there are commercial preparations for zooplankton you can purchase, both alive and preserved ones.