conversion

My 400 watt lighting system uses an hps bulb at the moment. The manual says it can use a mh conversion bulb. When I look online not all mh bulbs say conversion. Does it have to say conversion or will any 400 watt mh bulb work? Provided of course that its has the right base. Ty

~ There may have been post in the past discussing " how do you convert EC's to PPM's?"...I haven't seen it. so here is a quick and easy way to convert the numbers. ~ when following certain feeding guidelines given by growers or breeders they will suggest for an example : A. feed at 1.8 EC...

Currently I have two sets of the dual spectrum bulbs. I have heard of people using both spectrums at the same time, but I thought they were to be used at separate times, veg and flowering. Am I incorrect in this assumption? Also I have been looking into purchasing a HPS and MH setup in hopes...