you're going to need to adjust your pH frequently, like everyday, and an accurate read is the key to making the right adjustments. For instance.......

After you mix a batch of nutrients and water, you will probably need to raise your pH to the desired level (5.2-5.8) with pH up. After a day or so it will begin to rise up further than your initial adjustment and you will need to use pH down to keep it within the desired level. Everyday it needs to be watched and adjusted.If it gets above 6.5 you will see bad things start happening. Trust me, I know. Get a good pH tester, it will save a lot of headaches