What killed corals?

[DiZASTiX]

You may have some nitrate left but what you describe above is impossible, that nitrate rises after organic carbon dosing. It´s an artifact caused by the nitrate test method. Most likely your nitrate (and also the sum nitrate + nitrite) has decreased but the rise in nitrite completely hides the decrease when testing for nitrate.

Is it impossible even if there has been a mini-cycle arising from a large die-off?
However, what you mentioned came true: the nitrite just now dropped to 0.5 ppm, and the nitrate, 20 ppm!! Brilliant @Hans-Werner !!

 

[Hans-Werner]

If there would be a mini-cycle from a die-off I wouldn't expect that nitrate appears quickly. Nitrate is a kind of end and waste product that only appears when algae and bacteria are saturated with ammonium and there is still ammonium left. I would expect a lot of other things to happen after a die-off before nitrate appears.

 

[DiZASTiX]

@Hans-Werner , you know your ****. I applaud you. Thank you.

 

[futureinterest]

You may have some nitrate left but what you describe above is impossible, that nitrate rises after organic carbon dosing. It´s an artifact caused by the nitrate test method. Most likely your nitrate (and also the sum nitrate + nitrite) has decreased but the rise in nitrite completely hides the decrease when testing for nitrate.

This makes a lot of sense. Nice.

 

[Hans-Werner]

Thank you!

 

[vetteguy53081]

Chemistry was your enemy. If you are doing regular water changes, less need to add ALK, etc and enjoy your tank rather than treat it. If using auto-doser, lower the distribution a tad to prevent overdosing probabilities