Alkbud, your description of your grow room is very poor, using centimeters is not needed unless your a gnome.

How many 'plants' do you intend to grow with only a 250w HPS??

You can set your plants desired hight by growing it to your desired hight, although remember this, the plant does its best growing in the start of flowering, therefore grow past your desire so you should minimize it by about 3-4 inchs.

I can see you growing 1 or 2 plants under the 250w HPS, but I dont see more than 5-6.

The reflecter is simple enough, you can use any kind of home appliance you have, you dont simply need a glass mirror thats curved. You can use simply a piece of cardboard with boards on the back to keep er steady and mylar it. You could also bend the cardboard if you want to put it around the top of your light.
Starseed Reviewed by Starseed on . First Time Grower Needs Help with Growroom!!! first time growing and first time to post...plz help. growroom dimensions = 150cm/5ft Height x 60cm/2ft Width x 60cm/2ft Length light specs = 250W HPS first i need help on making a reflector for my 250W HPs since here in senegal you cannot find reflectors for 250W HPS weirdly enough, you find the bulbs and ballast but not the reflectors. In my total growroom height of 150cm, 30cm is already taken by the pot height and another 30 cm max at the top to maintain the maximum light intensity Rating: 5