We use a multi-ion meter from a cork based company called CleanGrow in ireland, www.cleangrow.com
You can measure and control individual nutrients, Ca, Cl, K, Na, NH4, NO3, Mg etc
Its the new way to grow
Check it out
Interesting nobody seems interested in measuring the actual nutrients in the tank, or the ratios of one ion to another, Ca:Mg, Ca:N, Ca:K all very important to control blooming and bud production, and the switch from vegetative growth to flowering
Just curious would any growers on here use a handheld multi-ion meter, so you could check up on the actual nitrate, ammonium, potassium, etc in your tank whenever you liked, to go beyone the crude EC measurement?
Cheers
NW