Did my Alk boost kill my fish?

[Eye H8 Empty V]

So I've had an Eibli Angel in mt QT for 3 weeks now and he's been a champ. I added a Desjardin Sailfin Tang yesterday and he was lethargic, probably from the FW dip and acclimation, but everything seemed cool. I checked it out this morning and my Eibli was in my overflow stuck to the chiller intake and the Sailfin is on it's side barely limping along. The only thing I did was test the Alk and it was 5.0. I added some buffer and it boosted it to 9.0. Would a 9.0 spike kill everything? The packaging said that it will not exceed 8.3 so you cannot OD. What this spike too rapid? Should I have left it at 5.0?

I'm so bummed out right now!

 

[EmdeReef]

Possibly a ph shock.

 

[LesPoissons]

5 to 9 is a big jump for most fish to handle all at once. What are your other parameters. Also were you treating your QT? Why was the fish there for 3 weeks?

 

[Eye H8 Empty V]

5 to 9 is a big jump for most fish to handle all at once. What are your other parameters. Also were you treating your QT? Why was the fish there for 3 weeks?

I'm going to mix a batch of saltwater right now so I can get the raw pH level and compare it to the alk dosed water. My DT is not ready so I figured I would get a fish or 2 in QT so the QT process will be completed once the DT has been cycled. I was not treating the QT tank with anything yet. The LFS that I got the Eibli from runs copper so I didn't treat the QT with anything. It's very simple, RODI, Salt(1.026sg) and a nitrifying bacteria.

I juts looked at the container and it's called Marine Buffer and it says it safely raises the pH to 8.3. I thought I was boosting the dKh. I have another container called Alkaline Buffer which is what I thought I was using. This is the problem with being disorganized and rushing to treat something that doesn't need treatment.

I had tanks 15+ years ago and never felt this bad from losing any fish. I don't know if it's because my 2yo son named him T (pronounced Tah) and would talk about him all the time, or that I'm more appreciative of life. Regardless I have felt so awful since this occurred. This could have been 100% preventable.