I do like throwing in crab shell, like a 1/4 - 1/3 cup per cu. Ft. bag #4. it last along time in the soil, calcium, phosphorous, chitin......lots of benefits to boost endo myco colony connection, strengthens early root development, keeps long term soil ph balanced. Like Bubba's ammended soil, as it dries the ph drifts up...this is what healthy soil is supposed to do!! Slurry numbers to verify, then guide you to the best feed Ph compared to the drift of the buffering soil. So crab is a safe and smart addition, especially when using RO water.