photo period situation?

I have just germinated some seeds using the paper towel method. transferred to rockwool cubes where they have been for about 6 days under florescent light they all have their first set of leaves 4 to be exact, my 1000 watt mh bulb just got here and i want them to have the most light available. How far away should i Position the seedlings from the light. Also because of issues with one of the tubes in the flourescent lamp I have left the plants on a 24/7 light period and i want to switch to 18 and 6 once i change to the mh lamp, can i do this with out affecting the strains( using femenized seeds cali dream) i also read that the 24hr light cycle can cause an unstable root system because the plants spend so much time in the process of photsynthesis. i do not know if this is true but so if someone can help that would be GREAT!!!

with a 1000 watter on seedlings id have it at least 4 feet away, but im no expert on such things. ive dealt mostly in floro. and switching to 18/6 should cause no problems at all.

You shouldn't have any problems changing from 24/7 to 18/6, but if you are going to use a 1000w MH keep it about a metre above the the tops of the plants and gradually reduce this to around 50cm once the plants have a stable root system and have been acustomed to the amount of light and warmth they are recieving. If you hang the light too close you could end up burning and dehydrating them to the point of no return, so be careful and just monitor your plants more often than usual until you become more familiar with your new lights capabilities.

Good rule of thumb:

Put your hands between the tops of the your plants and the light. If you can hold it there for a minute without it getting too hot for you hands the plants will be fine.


In regards to the seedling thats been under 24/7, yes you can change it to 18/6 and its better to do it earlier than later. It will cause some stress but not enough to worry about.