How close should I put my Metal Halide? MH HQI

[sjgsm]

I was curious as to how possible it is to have too much light for corals? My tank is 30gallons (30"w x 12 1/2"d x 18"H) and my metal halide is a 250W HQI Bulb type fixture. I felt before as if the light was pretty intense towards corals but it may have been something else in hindsight. It is currently suspended 22" above the surface which I am pretty sure is quite high. I plan on keeping pretty much all types of corals and want to know if I were to move the MH down to a given distance, about where should I place some of my corals I am worried about as well? I am planning on switching the bulb to a 20k (as my bulb is getting old) or in that kelvin range if that makes much of a difference.
Corals of concern:
Duncan Frag
Lunar Eclipse Zoas
Meteor Shower Cyphastrea
Frogspawn
Montipora Cap
Feel free to just add your opinion on distance of the metal halide or a certain type of coral you may have experience with. A lot of these corals are first timers for me and I know what websites say about placement and what not but they don't tell you based on a given light/tank size. Just trying to get this all figured out so I can get my tank going in the right direction. Thank you very much for reading my post and also thank you for any information in advance. Any help I can get would be much appreciated.
PS, here is a tank shot to give you an idea of my tank layout, The top left rockwork has been slightly adjusted so it is pretty much exactly as it looks in this photo.

 

[snakeblitz33]

I suggest no higher than 18" from the top of the water and no lower than 9" from the water. You don't have it placed in a canopy, so there is plenty of room for the heat to dissipate. If you put it closer to the water pay attention to your temp reading and make a few notes about the variability of the temp during the day. If it varies too much, then you should add a small fan. Of course, if you do you will have to make more frequent top offs.
Looks like you have a few algae problems right now. Maybe you could convert one of those filters into an algae scrubber and use some of the light from the halide to power the algae scrubber... hmm... research, research.