New fish died when I added to tank

Fishguy1079 · Jan 4, 2024

Hello All, so yesterday I got some fish online (a few chromis and hawkfish) for my 125 and within like 6-8 hours they were dead . I have a few fish in the tank already that I've had in there for a months. So I'm trying to figure out what I might have missed chemistry wise that would cause the new fish to die but the water not be so bad that the old fish are ok ? So with the new fish I of course acclimated them for over a hour( float bag in tank first, then put in bucket and slowly add water from tank every 5 minutes for about a hour then net and put in tank). Salinity around 1.020, temp like 76, Nitrate was 33, and PH was around 8.1. I know my KH is high and phosphates are high and the magnesium is low, but I've been adding magnesium increaser to try and get it to increase so it will hopefully level off the KH. Also I didn't think either being high was fatale to fish, especially in such a short amount of time. I had been having a issue with parasites and had previously used some ParaGard which dropped the PH, but that was last week and since the I've been checking daily and adding increaser if necessary and it's been around 8 for several days. There was still ParaGard in the water as the directions said to treat for like two weeks and I had a couple of days left. But I've never had ParaGard stress out fish enough to kill them , especially in like 6 hours. Any suggestions on what I might have missed or what I could test for would be appreciated. Thanks!

Jekyl · Jan 4, 2024

How long was the shipping? Did you add the water they came in to the bucket for acclimation?

Fishguy1079 · Jan 4, 2024

Jekyl said:
How long was the shipping? Did you add the water they came in to the bucket for acclimation?

It was just over night. They actually came in pretty fast got them by 10am . And yes I floted them in the tank first, then after like 15-20 minutes put them in the bucket with there existing water. Then I start adding water. Oh and the buckets are my fish only buckets(old salt buckets) that I only use for SW(water changes mostly).

Jekyl · Jan 4, 2024

chad 1079 said:
It was just over night. They actually came in pretty fast got them by 10am . And yes I floted them in the tank first, then after like 15-20 minutes put them in the bucket with there existing water. Then I start adding water. Oh and the buckets are my fish only buckets(old salt buckets) that I only use for SW(water changes mostly).

Was concerned because the water from the bag can actually become toxic. Not sure on the amount of time it takes. Better to temp acclimate, then match parameters in new water and switch rather than mixing them.

Fishguy1079 · Jan 4, 2024

Jekyl said:
Was concerned because the water from the bag can actually become toxic. Not sure on the amount of time it takes. Better to temp acclimate, then match parameters in new water and switch rather than mixing them.

Yeah, I know the bags can become toxic. That's why I never add the bag to my tank or quarantine tank water. But the fish were fine in the bucket, I think something was off in my tank I just can't figure out what. My first thought was maybe the nitrates were high(75+) and that could have shocked them while not really bothering my existing fish because they were already in the tank and it was gradual for them. But the nitrates were under 40 so I'm not sure honestly.