Did going hypo-salinity kill my live rock's bacteria?

[ntropics]

Hello. I had a recent quarantine tank problem that has resulted in two fish dying.
My QT was running successfully at 1.024 specific gravity. My Auriga butterfly fish, after six healthy weeks in the QT was transferred to the display tank, and is quite happy and healthy. Ammonia in the QT was always at zero.

As background, my QT has about twenty pounds of live rock in it. I treated the Auriga while in the tank with Metroplex, and Prazipro, for various presumed conditions. Retesting of water showed no increase in ammonia after treatment, and ammonia was zero until day of transfer to the display tank.

I purchased a black back butterfly from Live Aquaria, which arrived the same day as transfer of Auriga to display tank.. They ship at 1.020, so I dutifully brought the QT down to 1.02. I placed the acclimated fish into the QT, and it was dead within 36 hours. "Okay," I thought. "That is a hard fish to acclimate, so maybe that was the problem."

Two days later, I placed a Coral Beauty angel fish into the tank, another fish on my stocking list. (I suppose there may be some of you who might question whether I should have waited after death of fish.) The fish only nibbled (ate at LFS), and acted stressed. Day after introducing fish into QT, I tested ammonia, and it was at 0.25. Added Prime.

Next day (day two) the fish was dead. Removed fish. Ammonia was at 0.5. Now four days after that, the ammonia is still at 0.5 with no fish in the QT.

OKAY: So my question is: Could the sudden decrease in salinity have caused the ammonia/nitrogen eating bacteria on the live rock to have suffered significant mortality? It seems too coincidental that I drop the salinity, and the ammonia goes up, resulting in fish death.

Perhaps it would have been less risky to just bring the fish immediately up to 1.024?
Any other thoughts or suggestions? Thanks for any assistance you can offer.


Bruce
(200 gal FOWLR)

 

[Vinny Kreyling]

QT tanks are usually void of all rock. Only things that will NOT absorb any meds are used.
Like PVC. Do NOT place another fish in the tank without first sterilizing it to prevent any transfer from the previous fish.

 

[ntropics]

HI Vinny. Thanks for your response. I see you live in Miller Place. I used to live in Mt. Sinai, until I moved to Sacramento. Other than the snow and the traffic, I think Miller Place and Mt. Sinai are two of the nicest places to live in the country! I lived there until 2006. Believe it or not, when I moved there, there were only three traffic lights in town, 25A was single lane, and cabbage fields abounded. Not a good smell come late November!

So back to fish: There is no question in my mind: the live rock was not effected by the medications, because of the time that the fish was in QT after treatment. So that did not kill off the beneficial bacteria.

Now, not to hijack my own thread, but how the heck does one keep ammonia levels down in a QT without live rock? Before I used to put it into the QT ammonia levels were sky high, even with water changes. In fact, while we're on that topic, how do the fish stores keep their levels down if they are running copper?

So back to the original question: Can hyposalinity kill live rock if the salinity change is done over a matter of minutes?

 

[Michael Hoaster]

To keep ammonia levels down in QT, I add a scoop of sand from my display and a couple handfuls of macro algae.

I doubt a quick drop to hypo levels would kill your live rock. It may have some bacteria die off, but not all of it, and it would recover pretty quickly.