Sudden ammonia spike in QT

[Tbg299]

Several days ago, I did a 100% water change on my 20 gal QT because of an untreatable bacterial bloom. It has been running fishless for 2 months without any chelated copper. I have a lot of ceramic biospheres in there from my sump, as well as a sponge and mineral media in my Seachem Tidal 35 HOB filter. Yesterday morning, I got a Melenarus wrasse and and golden head sleeper goby. Ammonia was 0 in my tank when I added them. However, I checked the total ammonia today and it was 0.4. Seachem alert badge shows 0 toxic ammonia. Wrasse appears to be absolutely fine, but the goby has been breathing very rapidly since this afternoon. I dosed Prime this afternoon to reduce the ammonia levels, and I'm currently preping saltwater for a 25% water change. I also put a small airstone in to help the goby. I have no idea how the ammonia spiked so fast. My only guess is that I am experiencing a mini cycle because I deplenished a lot of nitrifying bacteria when I replaced all the water in the tank. Any advice would be appreciated.

 

[DrZoidburg]

Imo they can flat out die off or go dormant. Best to be careful with ammonia readings not every species is the same. You did what you can do. Everything you did, and water changes will help if it wasn't fatal damage. How did goby look in the store?

 

[Tbg299]

Imo they can flat out die off or go dormant. Best to be careful with ammonia readings not every species is the same. You did what you can do. Everything you did, and water changes will help if it wasn't fatal damage. How did goby look in the store?

I got him overnighted from Diver's Den (Live Aquaria). I did see his head twitch couple of times. I'm wondering if the ammonia is a non issue and maybe I should dose some PraziPro.

 

[DrZoidburg]

Just curious what kind of goby I wonder for other reason? For now maybe just let it settle in.

 

[Tbg299]

Update: ammonia spike resolved itself overnight. Ammonium went down to 0.2 after 25% water change and dose of Prazi Pro. Nitrites were 0 and Nitrates were 10 ppm, so nitrifying bacteria are populated.