Adjusting solution for initial PPM of water - Yay or Nay?

I have a question for some of you hydro vets.

So I'm in the tail end of my first grow in a GH Rainforest 66 (my journal has more details about it) and have been adjusting the PPM of my nutrient solution using a digital meter so I can get very accurate. I've been using tap water which is moderately hard, around 211 ppm. Since the beginning I have been assuming that I should absorb the initial ppm of the water into the total. So for instance if I wanted 900 ppm solution I would be adding 689 ppm of nutrient to the initial 211 ppm of the water to get a 900 ppm solution. That seems to be working fine for me. However I read on some other thread (can't remember where now) that the person always calculated the initial ppm of the water on top of the desired ppm of the nutrient level. So say they wanted a 900 ppm nutrient solution they would add that on top of the initial 211 ppm making a 1111 ppm solution.

So what about it folks...should you include the intial ppm in the total or sum the nutrients with the intial ppm

Any advice is appreciated.

Cheers

i always wondered the same thing... i personally would think to do it like you have been doing it. would be great to know what those with exp have to say though..

Mojo sounds like you going about it right!

hellraizer30 said:

Mojo sounds like you going about it right!

Click to expand...

Thanks. Its good to have a little validation. I'm super paranoid about over-doing the nutrients, but I wanted to make sure I wasn't missing something there and stunting my girls.

Maybe it differs between manufacturers? Canna says to add your tapwater base ppm's to the nutrient target. They suggest a base tapwater of 250. So if your tap is 250 and your goal is 900, your final reading should be 1150 (900 + 250).

Depending on the nutrient brand and your growing style, strain, and conditions, feeding under the "recommended" dose like you did may have been perfect for your plants in your situation. I hear that most often, the manufacturers recommendations are too high.

Ppm's are such a confusing topic for me. First you have all of the different conversion rates with the different brands of meters. Then, you have the manufacturer's feeding charts with the recommended doses that will likely burn your plants. Add in the tapwater base ppm equation. Then add in all of the posters who freely state their ppm's with total disregard to any of the previously mentioned things. It's enough to make a new person's head spin!

Once you learn to read your plants and watch their reactions its a lot easier.