Tank CRASH Day

Yesterday I noticed that the corals looked pretty much dead, today I saw NO FISH IN MY TANK!

Pre-change readings:

• NH3/NH4 = blue! - never saw this color before - off the charts!
• Ph = 8.2
• NO3 = 0-10 - can't tell
• Alk = 3.6
• PO4 = 0.00
• SG = 1.028

Massive waterchange was carried out (4 canisters (Ocean Spray) of freshly mixed water were PWC'ed.

10K K light stopped working sometime before the crash, so the tank was serviced by a single 36 Wt 50/50 light bulb.

1. Problem with the canister filter required its temporary shutdown (1+ month) with replacement by a HOB DIY Skimmer (from HOB filter). Strangely enough the week before the crash, all chemical levels reported normal (PH, Ammonia, Phosphate, Nitrate).
2. What I think were the leading causes of crash: 1. cansiter filter was restarted after 1 month of bein stale (stupidly enough, yes I admit I made a stupidity, I didn't toss the water out of it. Second, the sp. gravity level rose from usual 1.025-1.026 to 1.035+ (top of the scale and probably even higher.Strangely enough I couldn't find neither of my three fishes this morning! (could the cat gotten them? - I truly don't think so, could they have gotten dissolve in the high salt water?)

SO, to the conclusion.I'm not ready to give up on this hobby. I plan to restart. This time I will do the following:

1. Rescue the surviving corals [mushrooms] (tonight) by taking water measurements and making necessary adjustments. Will remove survivors off the live rock.
2. Will syphon through the top layer of the live (still live?) sand while removing the water.
3. Will remove live rock and will boil it to ensure all the aiptasias are GONE!
4. Will scrub-clean the front and side glass of whatever that brown crap had grown on it during the last few days.
5. Will ensure the canister filter and the skimmer function properly (flow adjustments).