Coco coir has been tested as a replacement for vermiculite in the PF-tek substrate, but it colonizes more slowly and is more apt to contaminate than vermiculite is. It needs to be sterilized longer. It performs poor in comparison with vermiculite.
Perlite holds far less water than vermiculite, you will to lower the water content. It has been used, but the results pale compared with vermiculite.
Grow wool (a hydroponic medium ) has been shown to work:
"An alternative (in my fun so far) is growool. It's 100% inert and pH neutral.
It's a glass fiber material. Same as insulation, but pH neutral and horticultural grade i.e. contains no fire retardants like monoammonium phosphate.
Holds 1/3 more water than vermiculite.
Colonises much the same as standard PF vermiculite cakes. Just pack it loose, as you do with regular PF vermiculite cakes -- a high air filled porosity profile is a must in any cake.
The top layer can be growool too. 100% vermiculite free cakes. Can be dunked after birthing like a regular cake. They weigh noticeably more. " Brown Rice Flour:
Dark rye flour has been reported to have favorable to excellent results when used to replace BRF (1:1 ratio) in the PF-tek, also other ground grains can be used like ground millet or ground millet based birdseed. Also corn flour. Wheat flour is not as good since it makes the substrate very greasy and clumpy, difficult to mix. Water:
In addition to any water suitable for human consumption(including mineral water) clean water from natural sources(river, pond) can be used.