How many pounds of grow rocks i need?

[Ron]

That's easy. 16 liter bottles cut in half would leave you with 16 - 1 liter bottles so you would need 16 liters of grow rocks or if you use the 16 oz solo cups, like I do, then you would need 16 - 16 oz of grow rocks. Make sence?
The weight will vary between brand names because some is more pores thus lighter than others.
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