The device is called iSpindel
was created by Samuel Lang.
The device is used in home brew but can be used on reef tank if do you have a quiet place on sump because the device can't be shaking all time.
The device should be a good alternative to measure the water density in a saltwater mix station.
I did a simplified version of iSpindel using the ESP-WROOM-02 Motherboard
but it's spending so much battery so I have to make some changes. For this reason I haven't published a tutorial yet.
The modified code to work with Ferduino is here: https://github.com/FernandoGarcia/iSpin ... -MQTT-only
You can find more information about this device here:https://hobbybrauer.de/forum/viewtopic.php?f=58&t=11826https://www.homebrewtalk.com/forum/thre ... er.598187/