What is my problem with RBTA's?

[tingram]

Hi,

I have bought 3 RBTA's from different sources over the past six months and seem to manage to do a great job of letting them die. One lasted a couple of months before giving up, it would even grab food from my hand when feeding.

They all seemed to find a good spot to stay, typically behind the rocks, before giving it all up.

Water quality is pretty good, unless there is something that I am not testing, or the tests that I am doing are inaccurate...

No Ammonia, Nitrates at 5PPM, Salinity at 1.025, temp between 79 and 81, ph at around 8.2...

I am using VHO lights at themoment, could that be a problem? I have 640W of them on my 6' 125G...

Please help me figure out my problem, I would really like to keep one of these, but don't want to kill off any more.

PS.
I also have a pretty big green carpet anemone that has been doing really well for about 8 months now, and my female perc just recently noticed it and now sleeps in it at night...

Thank You,

Tony.