What should I fill in the space between tiles on internal wall after installation with LATAPOXY® 300?

You can use LATICRETE® cement based grout (LATICRETE® 500 series sanded grout / LATICRETE® 600 series unsanded grout) mixed with LATICRETE® 1776 grout admix plus for filling these spaces (Grout joints) between tiles. You may also use SP-100™ Tile joint stain- free epoxy grout. For Industrial applications, use Industrial Epoxy Grout LATAPOXY® 2000.