I started with the drops, but found that the colors were not easy to interpret over the small changes within the range that I wanted to operate. Certainly a lot better than nothing, but a poor tool, for me at least, for more precise management.
After a cheap pen did what they usually do, I ended up with an Apera PH60 and love it. It has performed flawlessly for over a year now, and if that ever stops, a new sensor is half the cost of a new pen.
The indicator drops work out much dearer than a pen in the longer term if you use them a lot as I do, probably about $30 per year. They are only accurate from 5.5 to 6.5 once you are used to them you can tell the colour of 6 against 6.1. The thing is that a clean yellow is 6 and that is right where we want to be because it gives wiggle room on both side.
But there is something very satisfying about using colour. I talk about it in this part of my SWC explanation. You cannot use the colour patches on the bottle they are too extreme. The thing about pens that bug me is it is not at all unusual to have some sort of surprising pH shift, and when that happens the first thing I'd do is want to calibrate my pen, as I'm basically like a pilot flying by wire. I have to trust the electronics. But with colour you don't even have to think. Like if you open your eyes and there's a red apple and a green apple, you just see them, you don't think there's a red apple and there is a green apple.
All it takes is to mix up a solution of pH 5.7, 6, and 6.3 with plain water using a reliable pen and then use the indicator drops on each one and it is then easy to see very subtle difference, you can easily extrapolate pretty well once you see exactly the tint of those ranges. Say you see something that appears somewhere between a slight warm tint at 5.7 and a yellow at 6, well you know you're some where about the middle, and seriously you do not need any more accuracy than that I reckon.
It was all the calibrating that got me in the end I couldn't stand it. I only used a cheap pen and annoyingly it never really went out of calibration, but with every strange result I appreciated the confidence of the drops.
It's a choice between electronic precision if done right, and confidence. For me confidence give me more peace of mind. For example, it is entirely normal for me to have adjusted the pH and there's just a seedling in giant reservoirs so it's not really impacting the solution yet, suddenly there can be a massive pH shift and with the drops when I see that I just correct it, because I do not doubt the result.
I suggest using both Pen and drops together for a period of time, I know it's counter intuitive and the pen is easier, but it gives me more brain damage, each to their own. I always go for peace of mind.
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