measurement

Hi Everyone, I just wanted to mention an Android app that I use. It may be of interest to others. There are several apps that measure the relative intensity of each of the RGB components of lighting. But, I like this one as it's very easy to use and displays the relevant data in an attractive...

Thought someone told me how to do this about a month ago but I can't find the thread. Does anyone have a link or know how to calculate you magnesium if you know your calcium and gh? How are people usually calculating or measuring their magnesium?

Why is it that in order to determine the level of lighting, you need to measure the watts? I hardly ever hear anything about the importance of temperature in tank lighting. Couldnt you have a 36 watt bulb, yet the temp was way off, making the bulb less effective for growing plants? I might not...