Cloudy Water Ideas

[RuGlu6]

Last time i used BioPellets in established SPS tank I lost about $450 worth of my best SPS corals.
For the fish itch you may want to consider a UV light.
http://www.aquatraders.com/

As for the water change better to do more frequent but small water changes.

To drop Alkalinity add Magnezium http://www.jlaquatics.com/product/sc...+600+Gram.html
"Severely depleted levels of magnesium (below 800 mg/L) can cause depressed pH levels and an inability to maintain proper calcium levels. Magnesium depletion is commonly associated with the use of kalkwasser"

With small but frequent water changes your water chemistry will stabilize
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[Proteus]

Not sure how big your system is but I do two 5 gal WC a week on a 30g system and works great....for now

But as coral grows it will deplete the major three a lot more

And yes your feeding does affect po4. Try target feeding rather than broadcast