Scopa Tang died

[Koresample]

I have had a Scopa Tang for about 2 weeks now, got it at the same time as my LTA. He was doing very well, active eater, not skittish and got along well with the Skunk Clown. Yesterday he seemed to be hiding in the caves at the back of the tank, coming out only to eat, but ate very well still. Last night he seemed to stay in hiding in the back all night, and this morning when i went to do a water change, he was being devoured by my little crabs (blue legged hermits). i check my water almost daily, HG 1022, PH 8.3, AM 0, Nitrate 0, nitrite 0 and temp 79. When he first got in the tank i thought i noticed what looked like ich, but then it appeared to maybe just be microbubbles from my POS Sea Clone skimmer as they seemed to disappear. Does anyone have any experience with these fish or have anything else they might suggest i check? When moving my rock i noticed what appears to be a slime algae outbreak. I have recently started doing 5 gallon weekly water changes and switched from tap water to bottled water (measures 001 on my TDS meter) as well as added Fluval phosphate remover to my filtration. I have 49 lbs live rock and 60 lbs live aragonite in a 41 gallon tank. Total water movement is about 700 GPH. I am going to add a Hydor Koralia 2 600 GPH for extra flow and see if that hepls the algae problem, plus am shopping for a better skimmer.