Hello JHazzardB,
First just like to say welcome to the forum.
I think you already know that the tap water can be problematic, and not really a good choice for your water source. In some places their tap water is fairly good quality, but that's very few places. You should consider using a better water source or you may wind up with problems you can never get rid of. An example I like to use is if you start with the wrong ingredient's to bake a cake, don't be surprised if it doesn't come out right.
I know a lot of people like to use PPM/EC meters and feel it's imposable to grow good plants withough't them. But realistically their not necessary. In Over 7 years of growing hydroponically, I don't even have one and never did. They can't do the only thing I want them to. All you need to do is fallow the manufactures
nutrient mixing recommendations. In your case the
advanced nutrient calculator recommendation calls for 16ml per gallon (4 liters) of water for full strength nutrient solution. 1 Tbsp is 15ml, one tsp is 5 ml.
Now for seedlings I typically use about 1/4 strength nutrient solution. Then once they get bigger I step it up to 1/2 strength. Once they start to really get going bump it up to 3/4 to full strength. You can easily tell if the
nutrients are depleted or not strong enough by the yellowing of the newer leaves. How often you need to change the nutrient solution will depend on on factors like the water volume compared to size of the plants, as well as how much water the plants are drinking daily. Here is an article about
Nutrient solution reservoir size.
Quote:
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From knowing this, can I tell how many PPM of each nutrient I add when I raise my reservoir by the desired 900ppm?
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No it doesn't work that way. NPK is just a BASIC estimate. There are 16 essential macro and micro mineral salts needed for healthy plant growth.
Nitrogen (N)
Potassium (K)
Phosphorus (P)
Calcium (Ca)
Magnesium (Mg)
Sulphur (S)
Iron (Fe)
Manganese (Mn)
Copper (Cu)
Zinc (Zn)
Molybdate (Mo)
Boron (B)
Chlorine (Cl)
And Carbon, hydrogen and oxygen are absorbed from the air and water. The rest of the elements, called mineral salts/nutrients, are dissolved in the nutrient solution. NPK values wont tell you what any of essential mineral salt values are. Not to mention that you have no idea what the original PPM of your water supply consists of to begin with either. This is the bigest reason I don't use PPM/EC meters because that is what I want them to tell me. All the meters can tell you is the total concentration of everything, it cant break it down and tell you how much of each there is. PPM/EC meters can only tell you relative strength, that is the total of everything combined. If you want to know the totals of each element you need to have a sample sent out for lab testing. Another problem with PPM/EC meters are they are notorious for giving false increasing, even when cared for, calibrated, and stored properly. A decent meter will run $100 or more, and for $120 I can make 5,000 gallons of nutrient solution. I'd rather spend my money on nutrients, and by the toys when I get rich.
As for making your own nutrients, you can if you want to. I used to want to as well, but I don't bother even trying for one very good reason. Over the years I have compiled a list of
Cost Effective Hydroponic Nutrients that makes it not worth the effort to bother trying to make my own. The most cost effective ones cost less than 2 cents per gallon of full strength nutrient solution. I don't think I can even make them for that. And making your own isn't as simple as just fallowing a recipe. You really need some understanding of chemistry, and a really good scale.
Here is a recipe for tomato's from the
University of Arizona
Table 1. Fertilizer salts (adapted from Jensen and Malter, 1995)
Fertilizer Salts element supplied grams of fertilizer needed per 1000 liters of water to provide 1 mg/l (ppm) of the nutrient specified
Boric Acid [H3BO3] B 5.64
Calcium nitrate [Ca(NO3)2·4H2O] (15.5-0-0) N 6.45
Ca 4.70
Cupric chloride [CuCl2·2H2O] Cu 2.68
Copper sulfate [Cu(SO4)·5H2O] Cu 3.91
Chelated iron (9%) Fe 11.10
Ferrous sulfate [FeSO4] Fe 5.54
Magnesium sulfate [MgSO4·7H2O] (Epsom salts) Mg 10.75
Manganese chloride [MnCl2·4H2O] Mn 3.60
Manganese sulfate [MnSO4·4H2O] Mn 4.05
Molybdenum trioxide [MoO3] Mo 1.50
Monopotassium phosphate [KH2PO4] (0-22.5-28) K 3.53
P 4.45
Potassium chloride [KCl] (0-0-49.8) K 2.05
Potassium nitrate [KNO3] (13.75-0-36.9) N 7.30
K 2.70
Potassium sulfate [K2SO4] (0-0-43.3) K 2.50
Zinc sulfate [ZnSO4·7H2O] Zn 4.42
Also you need to know which chemical salts can be mixed with each other and which can't. For the same reason most liquid nutrients come in two or three parts. If they were mixed together in one concentrate some of the mineral salts would bond with others and wont dissolve in water so they wouldn't be useful to the plants. Here is a blog written by a chemist and hydroponics enthusiast, he has also created a free nutrient calculator called the hydro buddy to help make your own nutrients if you are still interested in trying.
Science in Hydroponics