I needed to add this smart monitor to a fish pond that i have, I remixed this drink floater to do this, the design was just perfect for my use. You can add as mush pontoons as you like and even arrange them as you like.

I got the sensor from Ali Express and it had every thing that i needed

• Testing 6 parameters at ones PH/EC/TDS/SALT/S.G./Temp
• WiFi enabled (Tuya app or Smart Life)
• Data Logger

however, the Water Tester was NOT waterproof with just about a meter (3FT) long of probe cable and 3 different types of them thus the remixed Pontoon. All of the probe will be submerged underwater to get the readings and the monitor will stay a way from the water with out butting any kind of stress on the cables when there is water movement (i my situation water is constant movement)

I merged the Pontoon Body & Cap together but if you like to get the max possible load (original design handled a max load of 1.2lbs with Hollow pontoons) you can split it to 2 different objects, and seal it with a balloon (see the last picture from the original design)

Printing: add 3 (more is better) parameters to keep the water out, keep the infill as low as possible to keep the weight low, PLA is fine as water will absorb temperature, but higher temp filament would be better