AdamHorton
Aquarium Advice FINatic
Hello. I want to run something by the experts here, mostly for a sanity check. TL;DR, two tangs died suddenly in my quarantine tank and I suspect it's because the hyposalinity treatment I did affected the cycle-bacteria in the tank, causing ammonia poisoning. I'm wondering if this is possible/likely and what I can do for future QTs.
Now, for all of the information.
The main tank is a FOWLR tank, 150 gallons + 30 gallons sump/refugium, started in 2009. Many fish have come and gone over the years but due to issues with my own health and global health the past few years I haven't added in any fish in the past 4-5 years. There are only two fish left, a damsel who has been there since 2009 and a 5yo mandarin. I want to restock the tank so recently I started out by getting two tangs.
I have a 20g tall quarantine tank that I set up, I did a fishless cycle over the course of two months and before adding anything to it, I was able to put 4 ppm of ammonia in the tank and have zero ammonia and nitrite readings after 24 hours consistently (I did this every day for a week). The morning I got the new fish I did a 100% water change on the quarantine, then I added the two tangs from the fish store (with an eggcrate divider in between. The tangs were both small, maybe 3in. long, one clown tang and one naso tang.
For 2.5 weeks everything went extremely well. Once the nervousness went away, both fish were eating very well and very active, showing no signs of disease or parasites. Over the first week I gradually decreased the salinity from 1.025 down to 1.009 as a preventative treatment -- in 13 years I've never once bought a tang that didn't have ich so I just did a preventative treatment, expecting to hold them at 1.009 for 4 weeks without symptoms, before bringing them back and putting them in the main tank.
Then one day, very suddenly, one of the fish died. The other fish was fine that day but the next day the other one died as well. I removed both fish immediately after they died. That evening I did tests on the water and there was a small but nonzero ammonia reading, with zero nitrites. I was confused. At the lower salinity I tried putting 4 ppm of ammonia in the tank and it took 2 days to get back to zero ammonia and nitrite after that. I can't really think of anything that could have happened to cause this issue with the bacteria in the system other than doing the hyposalinity treatment.
Since then I haven't added any fish to the QT, and I don't really want to add more fish to the QT until I know that I'm going to be able to give them the best chance possible at surviving. This fish store I'm going to now seems to do things really well, and these tangs were really healthy when I got them. The obvious thing is to just try again and not do hyposalinity unless I see signs of ich, but I'd at least like to do my due diligence and find out if there's anything else I should be looking at that could have caused this.
Right now the QT is at 1.025, and I'm just increasing the amount of ammonia I can add while getting back to zero ammonia and zero nitrite within 24 hours. I'm at 5ppm at the moment.
Any thoughts are welcome, I can give more information if needed. Thanks.
Now, for all of the information.
The main tank is a FOWLR tank, 150 gallons + 30 gallons sump/refugium, started in 2009. Many fish have come and gone over the years but due to issues with my own health and global health the past few years I haven't added in any fish in the past 4-5 years. There are only two fish left, a damsel who has been there since 2009 and a 5yo mandarin. I want to restock the tank so recently I started out by getting two tangs.
I have a 20g tall quarantine tank that I set up, I did a fishless cycle over the course of two months and before adding anything to it, I was able to put 4 ppm of ammonia in the tank and have zero ammonia and nitrite readings after 24 hours consistently (I did this every day for a week). The morning I got the new fish I did a 100% water change on the quarantine, then I added the two tangs from the fish store (with an eggcrate divider in between. The tangs were both small, maybe 3in. long, one clown tang and one naso tang.
For 2.5 weeks everything went extremely well. Once the nervousness went away, both fish were eating very well and very active, showing no signs of disease or parasites. Over the first week I gradually decreased the salinity from 1.025 down to 1.009 as a preventative treatment -- in 13 years I've never once bought a tang that didn't have ich so I just did a preventative treatment, expecting to hold them at 1.009 for 4 weeks without symptoms, before bringing them back and putting them in the main tank.
Then one day, very suddenly, one of the fish died. The other fish was fine that day but the next day the other one died as well. I removed both fish immediately after they died. That evening I did tests on the water and there was a small but nonzero ammonia reading, with zero nitrites. I was confused. At the lower salinity I tried putting 4 ppm of ammonia in the tank and it took 2 days to get back to zero ammonia and nitrite after that. I can't really think of anything that could have happened to cause this issue with the bacteria in the system other than doing the hyposalinity treatment.
Since then I haven't added any fish to the QT, and I don't really want to add more fish to the QT until I know that I'm going to be able to give them the best chance possible at surviving. This fish store I'm going to now seems to do things really well, and these tangs were really healthy when I got them. The obvious thing is to just try again and not do hyposalinity unless I see signs of ich, but I'd at least like to do my due diligence and find out if there's anything else I should be looking at that could have caused this.
Right now the QT is at 1.025, and I'm just increasing the amount of ammonia I can add while getting back to zero ammonia and zero nitrite within 24 hours. I'm at 5ppm at the moment.
Any thoughts are welcome, I can give more information if needed. Thanks.