Will a phosphate reactor help at all?

I found that when I first got into reefs using 2 x 175w over my 70g (18" deep) I could not get good color. Now, if everything else is perfect, they might be ok, but I've never seen a tank that was perfect (well, not many). The first thing you need to realize is that it can take 6 or more months just to build up stability in the tank so that SPS will grow, let alone color up properly.
When I switched to 2 x 400w, my colors got better, but it wasn't until I had a couple of years experience watching my acros turn brown before I could start getting nice colors. You need to make sure that nutrients are 0, pH, Ca and Alk are in range and stable. Flow is important for growth, not so much for color. If you put softies in the tank, it could impact the SPS growth and general happiness. The problem is there are so many things working against you, you really need to know your tank very well. This takes quite a while.

I feel like I should say something about 175w MH lighting. I use 175w MH on my 24g cube. Yes my cube is 18" deep, but I do find I get good coloration throughout the different levels of my tank. Of course the higher the frag the more "intense" the coloration is. I feel I get good coloration from my lighting, but I attribute it to both a high bulb quality, and having chosen a spectrum that works with my existing lighting. Like Reef_raf said, 175w didn't work for him, but it worked for me, so its all about what works for you.

Mik, what everyone is saying is that 175w MH isn't necessarily the best, and that it has worked for some, and not for others. Before you go looking at upgrading your lights or anything, we're saying you should focus on your water quality.

From what I've been following here is what I would do if I was you.
1) Get my water parameters under control and maintain them for at least 3 months before adding anymore SPS.
2) Step back and reevaluate your set up. How are you existing SPS doing, what about your livestock. Are you seeing growth and color in your SPS? Are you fish thriving? I know you take photos of your setup, so consider keeping a "photo diary" of your existing frags, and see if they grow, color up, or brown out. From there you should be able to ascertain where you need to go next, whether its a lighting upgrade, or something else.

To answer your original question about SPS and flow, this is how I understand it works. Flow helps because it gets the SPS, and LPS to extend their polyps. The heavier the flow the thicker branches seem to appear in SPS because they must withstand the force of the flow. SPS are found on few different types of reefs, each with their own flow and ebb patterns. Flow helps reproduce the natural environment, it provides circulation through branches, and even brings nutrients and disposes of waste. More flow is better, to a point. In my experience, and my tank, my sps like to wave a little, but its just that my experience. Pick up Borneman's Aquarium Corals book, its invaluable in helping you educate yourself on what your keeping, and what we know about these creatures.

A phosphate reactor, using a phosphate remover, will only remove phosphates, it would necessarily give you better coloration.

Mik can I recommend investing in this book. It will help you a lot and you will begin to understand the proccess and theory
The Reef Aquarium Volume 3 by C. Delbeek & J. Sprung

Every store has it and it will save you a lot of money in the long run

J

I second this recommendation, its also an awesome book.

Catherine, just to be clear, I'm not saying that 175w don't work, I ran them for a long time with decent results. Only when i went to bigger lights I got better color. I was able to upgrade at the time for no cost to me, so I wouldn't recommend throwing away 175s to get something else.

Ouch. Kind of pricey. Is their anyone that I could borrow it from?

Try Amazon.ca, or Chapters. They are often considerably cheaper then in stores.

Hey Mik,, , I know these books seem really expensive but the wealth of information that they provide you will end up saving yoou so much money and disapointment in the long run that they will easily pay for themselves. Books can be some of the best investments you'll make in the hobbv.

A lot Cheaper then the $250.00 you are going to spend on a ballast

J