The free shipping is only on the build your own reef cleaner package.
Why not skip the astreas and get the mexican turbos?
I also recently purchased from them a couple months ago and ordered 12 astrea( never gonna do that again) 12 nassarius, 6 mex turbos, 1 atl cuke, 1 serpent star, 1 sand sifting star, 1 arrow crab , and 1 emerald crab. I bought all this for a 90 gallon dt + a 30 gallon sump. So I would say 6 nassarius, 3 mex turbos, and 6 astrea if you still want to go with them. The best snails that I bought were the mex turbos because their always cleaning the glass. The nassarius are next always cleaning the sand bed. The astrea's however barely move and their always falling on their back so I have to flip them back up.