Because silica sand is born from fire/high heat you can be sure it is sterile. River sand or plaster sand is not always clean enough.
Is it necessary to use silica sand or is river or sandbox sand OK?
Welcome to plantspearlsparanoia. As primarily a seedling producer, I can not emphasize enough that quality seed will always be a requisite. To achieve repeatable results, your actions will need to be carefully done with attention to detail.
The soil needs to satisfy the seed and subsequent seedling with air, water, and good drainage if you are to be successful. That being said let’s talk about the soil and what constitutes a good germinating medium. Some of you may tell me you dig the soil up right out of the garden and are successful. If that works for you, great, but I require a clean medium and I usually blend it myself. My mix contains peat, perlite, coir, and #16 sand. I mix a bench at a time and give you the ratio which you can adjust for the amount that you are going to need. 3cuft peat-12cuft perlite-1cuft coir(shreaded coconut hush fibre) and 1.5 cuft #16 silica sand.