natural scource of mg and cal for my dwc system

[Bio boy]

im running a bio systemish onlyusing lucas but i try stay away from addatives, and il need mg and cal somepoint and want to add them safely without the chemicals,

how can i add this? ive heard of egg shells or somthing but..

im totaly suspended in water no soil,

also lucas lacks mg somtimes, woudl i be best to find a scource of slow released mg before i get problems>>??

 

[mg75]

there are plenty cal mag + iron supplements including organic ones. GH has calimagic if you want to stay with the same manufacturer. most calmag additives do contain some nitrogen, so do account for that with certain strains.