Agree with admin. 
  
I personally mix a batch every time I feed. I mix small quantities (1LT) at a time, based on my container sizes. I know its more effort and mixing really small ratios, but I can adjust every time I feed. 
  
I use a small 5ml syringe to measure 0.5ml,lol 
  
Its seems to be working for me. 
  
Interested to find various techniques for mixing nutrient solutions.