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Re: pH meters and controllers

First you need to decide which it is you want. There is a big difference 
between a pH meter and a ph controller. If you simply want to check your pH 
like you would with a chemical kit, then get a meter. The only reason to buy 
a controller is if you are injecting CO2 and have a solenoid on your CO2 
setup and you want electronic control based on the pH value in the tank. Most 
controllers also have a continuous pH level readout. So if you look at it 
this way, a meter is a single function device (pH level only) and a 
controller is a two function device (pH level and turns solenoid on/off). In 
general, hobbyist level pH controllers cost more than hobbyist level pH 

I have used digital pH pens, and these need to be calibrated every time you 
use them. Not worth the time to me, and I don't believe thay are very 

I don't have experience with the silicon chip types mentioned in an earlier 
post on this topic.

I prefer the type of meter/controller that uses an in-tank probe, usually 
Ag/Cl, which has a cable several feet long that connects to a remote 
meter/controller via a BNC connector. This allows continuous monitoring of 
tank pH and you can place the meter/controller wherever you want. Mine are 
mounted on the inside of the tank stand doors. I use 4 controllers in my 4 
planted tanks. The probe is the only piece you need to replace, and mine 
usually last 18-24 months. Replacements are $34 US by MO. I calibrate my 
meters every 4 months or so. 

IME the best all around pH controller regarding function and price is 
manufactured by Milwaukee Instruments, specifically Model SMS 122. This 
controller costs about the same as similar style meter only units made by 
other companies (American Marine, for example). It comes with meter, probe, 
calibration solution, control module, and A/C adapter to plug in the wall. 
Complete. I own and use three of these, and am completely satisfied with them.

This unit can be purchased for $99 at www.spectrapure.com. That is where I 
bought all of mine. Great company. A bargain for a controller. You could just 
use it as a meter if you think you may add a solenoid to your CO2 injection 
setup in the future.

You can spend thousands on pH monitors and controllers, depending on the 
level of accuracy and features you want, just look at scientific equipment 
supply catalogs. Most hobbyist level meters/controllers are not lab grade and 
don't need to be. Most hobby level meters/controllers are accurate to within 
+ or - .2 units of pH. Perfectly acceptable for a planted tank.


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