Lets talk about your water:
I think you could spend your life studying water - seriously. But lets just keep it simple. First we need good tools. Three things we are concerned with PH, Salinity and Chloramines? A EC meter will tell you the salts (dissolved solids). Most nutrients you can get made for cannabis can work with water <200 PPM, Advanced Nutrients wants <10 PPM. Some nutrient vendors make a high PPM base fertilizer up to 300PPM. Generally speaking <200 PPM and you are good for tap water. If you are over this you need to blend in RO or DI water to get it under 200 PPM. If you are less than 50 PPM you may need to add some Cal-Mag to bring it up to 50 PPM. Ok a $10 TDS meter can tell you this but It is not good for testing nutrient levels for that you need an EC meter and good ones cost more. An EC meter will also measure TDS.
Next is Chloramines. Chloramines are formed when municipal water is treated with chlorine AND ammonia to sanitize the water. Check your local water report and look for ammonia in the sanitizer portion. Chloramines do not dissipate in the air and they are not good for your grow environment. It is very easy to treat for it. Just use ascorbic acid.
Chloramines Removal
You are looking for ascorbic acid - vitamin C. The store brand is usually the cheapest without other stuff added in. 50mg per gallon will treat water with 3.8 PPM of chloramines.
Finally is PH I saved the hardest for last. I have had more problems in grows caused by PH than any other factor and it has been costly. So spend money on good tools and take care of them. In soil, coco and mixes you need to know the PH in the root zone. Run-off is too unreliable. A good probe is the Accurate 8 (the knock works ok) or a Blue Lab Probe (they have different styles for soil, coco and rock wool). Then you need a probe designed for testing the PH of the nutrients. I don't know how to emphasize how important this part is to successful growing. Learn from my mistakes.
ok so almost 8 gallons; this is better but when you have 4 plants at 5 weeks old they may drink 3-4 gallons a day and what happens is the nutrients in the reservoir get stronger and stronger as the water is used by the plants and unused nutrients get flushed back into the reservoir. If you do not monitor the PPMs rigorously you can go bad in a short period of time.
