After adding the nutrients, let it settle for an hour or two before checking pH. Optimum pH range is 5.5-6.5 (6.0 is ideal) Keep the solution between 65-75 degrees (60 min, 80 max).

Nutrient solution and solution pH influences on onion growth and mineral content, J. Plant Nutr. 2006; 29(2), 375 – 390. doi: 10.1080/01904160500477028. 11. Fakhrurroja H, Mardhotillah SA, Mahendra O, ...

Maintaining the recommended pH levels for your hydro grow system is also key to your plants’ success. A slightly acidic pH will help promote the growth of beneficial fungi, which is great for weed.