Ive got mineralized topsoil for sale $4 a liter. 1 liter is good for a 10 gallon tank, it includes potash and micros. Shipping depends on how much you buy, i will ship flat rate. I can ship 6-9L for $14.35, 10L+ for 19.95, both with tracking. The formula i use is length of tank in inches X width of tank in inches divided by 160 will equal the number of liters needed to make 3/4 inch depth of the mineralized topsoil.
Get it while it lasts.