You may use CSF if they are from fetal sources. However, spin it at 12,000rpm in eppendorf aliquots to precipitate any possible cell debris or particles. Take upper clear fluid into a lager tube together. Add 1 mg glucose, PenP+ StrepM mix/ml CSF to maintain ES cells. Mix well, make aliquots and store 4C until use. If you obtained from adult, you may need some other GFs for induced neural differentiation.