Help with water quality - I need your expertise:)

[daceman]

I've had my 55G tank set up now for 10 months...and about 1.5 months ago accidently dumped a bumch of Kalkwasser mix chnage water into my sump....which killed almost all my inverts & the few corals I had. The plants turned white.
Now, I keep checking & monitoring my water conditions and still can get it back to a good level. Plants, inverts & corals still instantly die (I thought things looked better so I just purcased a hermit crab...and found I was wrong). My water conditions are
Nitrite - Basically zero (ranges between zero & .5)
Nitrate - 40 mg/l
Ammonia - 0 to .25 ppm (tests say safe ranges)
Alkalinity - 4.5 mg/l
ph - 8.4
Copper - zero
Phosphate = basically zero (.1ppm)
Calcium = 200+ (seems low & I continue to raise in conjunction with Mg below)
Magnesium = 700 ppm (I'm continuing to raise)
Silicate = 0

What am I missing? Is my Mg and Calcium shortfall the reason these inverts keep dying? I'm getting really frustrated & need some expert advice.

[MalHavoc]

What is your salinity?

Your ammonia should read 0. Even a tiny amount is deadly to invertibrates.

Nitrite should also be zero. Undetectable.

Your nitrate levels are way too high. 40 ppm would probably be extremely unpleasant for most corals.

Your calcium should be ~400 ppm, and magnesium should be right around 1200 ppm. You can get to this with water changes.

A phosphate level of 0.1 is not "basically zero" - it really needs to be less than 0.02 ppm in order for corals to really thrive, especially stony ones.

ARe you using RO/DI water? Tap water shouldn't be used when you do water changes. Are you doing water changes? Try to change 10% a week, until your tank's measurements start to look better.

[daceman]

Salinity is 1.017
thanks. Anything else I need to check for that might be cause of turning plants white?

[LtSmash]

Your Salinity seems a bit low, 1.023 to 1.025 is the norm

[MalHavoc]

Actually, no, 1.025-1.027 is the norm, especially if you want to keep invertibrates like coral. Fish can tolerate lower salinities because their bodies can regulate that on their own, but corals and things like anemones cannot.

If your specific gravity is really that low, I'd bet that you've found one of the biggest reasons why things aren't living in your tank.