With all the different brands of nutrients on the market today, the  question always comes up, witch ones to get for the best performance?  But growing good, productive, healthy plants is more complicated than  just simply picking a good quality brand of nutrients for the type of  plants you want to grow. There are a lot of good quality nutrients on  the market. But the first thing growers typically blame is the nutrients  if they wind up with poor plant performance. Then they usually just  decide to try another brand, and go on another quest looking for the  best one. But before changing brands, there are some things to consider  before blaming the nutrients for causing the poor plant performance. 
First Tip
 
The first important factor is volume of your nutrient reservoir. That is  deciding how many gallons of nutrient solution you need for each plant  in the system, total in the reservoir. Larger plants use more nutrients  and water than smaller plants do. So use your plants as a guide as to  how much nutrient solution is needed to properly supply them with what  they need. For instance for large plants like tomatoes you should  estimate at least 2.5 gallons of nutrient solution per plant in the  system. For medium size plants like peppers or basil estimate at least  1.5 gallons of nutrient solution per plant in the system. Then for  smaller plants like strawberries or lettuce estimate at least 1/2 gallon  of nutrient solution per plant in the system. Then multiply that by how  many plants you plan to grow in order to give you a minimum reservoir  size.
This is important because larger volumes of nutrient solution will  have smaller fluctuations in their nutrient concentrations as the plants  use them up. Basically this helps keep the nutrient solution evenly  balanced as the plants deplete the nutrients from it. Also in warm/hot  weather the plants transpire (use) more water than they 
do in cool weather. As the plants use up more of the water from the reservoir  than usual, this concentrates the nutrients (EC levels) that are left  in the solution. With smaller water volumes there is a much better  chance of nutrient levels soaring to toxic levels/concentrations. Even  when regularly topping off with fresh water to the original volume in  smaller reservoirs, there is a lot of fluctuation of the nutrient  concentrations that wont do your plants any good.
  cool weather. As the plants use up more of the water from the reservoir  than usual, this concentrates the nutrients (EC levels) that are left  in the solution. With smaller water volumes there is a much better  chance of nutrient levels soaring to toxic levels/concentrations. Even  when regularly topping off with fresh water to the original volume in  smaller reservoirs, there is a lot of fluctuation of the nutrient  concentrations that wont do your plants any good.
Second Tip
 
There are a lot of variables that can affect the amount of nutrients the  manufacture recommends to use (dosage). Of coarse some trial and error  here can be helpful to you in the long run, but you should start with  what the manufacturer recommends. After all, they know their nutrients  best. Some of the things that can affect the dosage that the nutrient  manufacturer recommends to use are plants size (seedlings, small plants,  heavy growth etc.), the plants growth phase (like vegetative growth or  flowering/fruiting growth), type of growing medium (clay pellets, Coco  cor, Perlite, Vermiculite etc.).
Even the type of system like recirculating or non-recirculating  systems can make a difference. Most manufactures assume that your plants  are going to be grown in favorable conditions, so they don’t always  post directions for weather extremes for those people that grow  outdoors. But like I mentioned earlier, the plants will take up more  water in hot environments, and going a little under the recommendations  (dosage) for hot conditions is generally recommended.
When  mixing your nutrients and/or additives, add all the water (at least 3/4  of it) to the reservoir first. Two and three part nutrients are  separated for a reason. If you pre mix them in concentrated form or even  small amounts of water first, some of the elements in the solution that  were separated now have a chance to bond, and a white precipitate  (calcium sulphate) may even be seen forming in the solution. By  thoroughly mixing each concentrated part of the nutrient (and/or  additives) one at a time into the larger volume of water will keep them  diluted enough so they wont have a chance to bond together. If they do,  they will become un-usable to the plants.
Forth tip
 
Keep your nutrients mixed up. For most systems this wont be much of a  problem, using a air bubbler in the reservoir will easily keep the water  moving. Also most systems that recirculate the nutrient solution should  also keep the water mixed up enough. This keeps the mineral elements  from settling and concentrating at the bottom. This also prevents  areas/pockets of high or low pH levels, where the mineral elements then  become unusable outside of the plants pH range.
Fifth Tip
 
Check your pH often. Plants are only able to uptake the nutrients in the  solution if the pH is in the right range. After mixing your nutrients  immediately check the pH, and adjust it if necessary. Then recheck it  until it’s right. After that checking it daily would be recommended.  Letting the pH go out of range will deprive your plants of nutrients,  and allowing pH to rise above 6.5 can often cause the white precipitate  to be seen in nutrient reservoirs also.
Conclusion
It’s not just having good nutrients that maters, it’s also how you use  them that makes the most difference in their performance. By taking the  time to regularly fallow a few basic guidelines, as well as checking the  manufactures instructions, then fallowing their instructions correctly.  You will be able to get the most out of any nutrients you choose to  use. Growing good hydroponic plants requires a little more work than  just pouring some water on a mound of dirt, but well worth the effort.
