Complete Tank Crash

[waschuppp]

After a long winter of not taking good care of my reef tank, I started to do better this summer and now all of a sudden things died. Everything was fine after I added 3 SPS corals (montipora spondoges, chalice, and a green encrusting coral) which I added to lower my Calcium and Alkalinity levels along with the Magnesium.
Everything was fine and the levels were going down until one day I was testing water and scrubbed a bunch of built up algae and soon my two clownfish started acting weird down in a corner and both died over the span of 2 hours along with the montipora. However my cleaner shrimp and two other SPS corals were fine. My water became a bit cloudy and I let the tank be for a week.
Come yesterday, I tested my water and the parameters were fine (nitrate, calcium, alk, and magnesium) so I bough a bunch of crabs and snails along with a torch, Duncan, Zoa, and war favia. The next day I wake up and no snails have moved and all look dead, and all of the coral died.
Note that the day my clownfish died I made the stupid mistake of not rinsing the test tubes before putting the back in the tank to test more water.
Could this crash could have come from bad chemicals coming in? Toxic algae? I have absolutely no idea. All of the parameters are fine accept for a little too low nitrate if 0-5. Anyone have any idea? Any solutions?

 

[PPBlimpy]

How long had the tank been set up and did you disturb the sand bed much?

not sure how likely but wondering after a long winter of minimal maintenance, and possibly minimal CUC i wonder if you hit some sort of pocket while cleaning the tank? i dont think the remaining stuff in the test tubes could kill off everything.

 

[waschuppp]

How long had the tank been set up and did you disturb the sand bed much?

not sure how likely but wondering after a long winter of minimal maintenance, and possibly minimal CUC i wonder if you hit some sort of pocket while cleaning the tank? i dont think the remaining stuff in the test tubes could kill off everything.

It’s been up for about 2 years and I don’t really think I disturbed the sand bed.

 

[waschuppp]

I forgot to add that I have a certain type of macro algae that can do sexual reproduction in response to water quality changes and cloudy up the water like mine is. But is so harmful that all fish and coral die?

 

[SilverGryphon]

Do you have a glass heater? could it have gotten damaged? Stray voltage in the tank would cause the sudden death.

 

[Tahoe61]

Why did you want to lower alk and calcium? Were you dosing and not testing?
If the water is cloudy suspect a bacterial bloom and the possibility decreased oxygenation.
Did you test for ammonia?
Without you posting actual values for chemistry it's a crap shoot and pure speculation as to cause.


Sorry this happened to you.