Hi all,
I wouldn't buy it. The main reason is that it can't be calibrated "
Calibration: Manual (pre-calibrated)", and this means that you have no idea of whether it is working or not.
These type of meters are fine for very salty, extremely acidic or alkaline solutions, but as soon as you get anywhere near pure H2O, or around pH7, they are worse then useless.
If you really want a pH meter, you need a meter with a silver chloride or calomel reference electrode and pH4 & pH7 buffers. A Hanna one for about a £100 works reasonably well, but still needs some maintenance of the electrode, and setting up before use.
You can't just dip any pH meter into a tank and get a meaningful reading. <
http://www.ukaps.org/forum/viewtopic.php?f=37&t=19401&p=196512&hilit=pH+meter+Darrel#p196512>
I've got a lab full of pH meters (including bench meters costing £1000's of pounds), but I virtually never read the pH of the tank water, it just isn't a very useful measurement without some other water parameters (particularly conductivity and dKH).
You can buy a cheap TDS meter and this will be both accurate and you can use it as a dip meter. This is all I do.
cheers Darrel