wtb phytoplankton

I am looking to try some thing in my sump I want too grow phytoplankton in there. I will be placing it in a Dip and Pour Fish Specimen Container use a air line with a air stone to bubble and keep it agitated. The light for the sump to keep it growing. I will be taking out a turkey baster full a day to feed to my tank and add a turkey baster full of water. Should I use my salt water or would I be better of to add a cup of ro/di water each day?
So I am looking for a small amount to get started hoping for someone here in the Quad Cities or close by to have some.
post here or pm me Thanks