I would agree with the tread you have read. The UV will kill anything that passes through it....including plankton (coral food) and micro organisms in your water. Most of the criters that do the biological filtration in your tank are microscopic.....a UV sterilizer will kill alot of these beneficial bacteria. So it is counter productive....on one hand you have a sand bed full of bacteria doing your filtration, then on the other you have a UV trying to kill the bacteria....
IMO the UV is best left for FO tanks with shallow sandbeds, with little or no live rock.
One more thing....
I don't know how much a UV will help with hair algea, as it can not do anything to aid in the removal of phosphate from the water. Infact if anything a UV will kill some of the bactera that do perform the nitrogen cycle. UV's are GREAT at killing parasites like ICK and harmfull bacteria, but I don't think they will help with algea.
Please someone chime in that has more info...I maybe completely wrong about these things as I am speaking only from information gleaned from other folks over the years.
I'm not sure it will help with the hair algae either? I have a friend of mine that has a backyard pond & ever since he added a UV his pond looks great no more algae at all. I figured that if it works that good with a FW pond it would also help with SW. I planed to place it between my return pump & tank?
"Most of the criters that do the biological filtration in your tank are microscopic.....a UV sterilizer will kill alot of these beneficial bacteria. "
Most of the bacteria that perform Nitrogen cycling will be sessile on larger particles such as sand, rock, settled detritus, glass, etc.
The environments we create in our tank skew bacterial growth potentials to allow concentrations of in water bacteria to rise way above natural, and in proportions that favor potentially virulent bacteria.
I would personally choose to use UV sterilization on a reef system. Our coral culture systems run UV.
You may need to run the UV off of a powerhead or small pump for maximum effectiveness as many UVs are not rated to handle the water volume of most of our return pumps. Depending on the size of the UV the fittings may be too small and reduce flow back into your display. If the water passes through the UV too fast it doesn't have time to kill the organisms you are trying to get rid of it just kinda gives them a "sunburn". And it did greatly help with diatoms in my tank. I'm not sure about hair algae.
IMO, UV filter is fine. It only pulls and filters from the water column. Since your beneficial bacteria and algae grow on your LR and other surface media, the UV should not have a negative effect. I run a 12w with my 75 gallon with no problems.