Fish loss during acclimation

[Cheez13alls]

Tank size: 20 gallon
tank age: 7 months
pH: 7.4
ammonia: 0 ppm
nitrite: 0 ppm
nitrate: 20 ppm
tank temp: 74 F
(unfortunately I do not know the kH or gH of the tank)

I've never posted on a fish forum before but I felt it necessary due to this recent event that has me absolutely stumped. I just recently purchased some Pearl Danios from a local pet store and started to acclimate them. I did a drip acclimation for about an hour. At first everything was going fine but after about 30 minutes I noticed one of them turning a dark color. After some time it started flipping upside down and it looked like it was gasping. I did an insane amount of research while trying to figure out what was wrong. I stopped the drip acclimation and isolated the one fish thinking maybe it was just the one, since the rest seemed to be fine. After a while they all started to act strange and shortly followed the same symptoms the first one did. After doing some research I think it was due to "osmotic shock" or "pH shock". I am thoroughly confused to what went wrong. If it was from osmotic shock then why, if it wasn't then what would have caused this. I am also curious to know if this was entirely due to my own negligence or if it was from the pet store. I should add that I do weekly water changes for my tank and test regularly. Currently I keep plants, ghost shrimp, and ramshorn snails which all are healthy and actually doing really well. I only add dechlorinator and some fertilizer for my plants into the tank weekly.

As a side note: I have been struggling to keep the nitrates down in my tank. So weather or not that is the problem if someone could tell me how to reduce those that would be great.

I appreciate anyone who has the time to read this and/or comment

-J, aka Cheez13alls

 

[Colin_T]

Hi and welcome to the forum

What is/ was the nitrate level in the tank?

Check the tap water for nitrates. if it is 0ppm, then do a 75% water change and gravel clean the substrate every day until the nitrates are down to 0ppm. Then do it once a week or any day the nitrates are over 20ppm.

---------------------
Contact the shop and tell them about the fish dying in the bag.
Ask them what the pH of their tank water is.
Ask them when they got the fish in?
Ask them when they did a water change on that tank?

If the pH was significantly different, that could kill the fish.
If your nitrate was extreme (above 50ppm) that could stress and kill them.
If the shop had done a water change that day or the day before, that might affect the fish.
If the fish had only come into the shop in the last day or two, that could affect them.

 

[Bruce Leyland-Jones]

Adding onto @Colin_T 's advice, I'd also be curious about the parameters the fish were sitting in before you started your drip acclimatisation.

Personally, I'm still in two minds about the efficacy of drip acclimatisation, based on my following thoughts...
The fish are transported from their shop tank in a plastic bag and, for the duration of the journey, are sitting in their own waste.
Often this shouldn't be an issue, but for more active and/or stressed fish, this might be.
Assuming tank parameters are not too dissimilar from their tank of origin, I'd be inclined to remove them from their toxic waste asap.

My preferred method of transferring fish from bag to tank was/is to float the bag to equalise temperatures for half an hour and then to pour the bag through a net into a bucket. The fish then goes straight from the net to the tank. For the tank itself, I switch off the lights for about an hour, to give the fish a chance to find a hole to de-stress.

I was pleased to find that I was not alone in my thoughts;
KGTropicals and Acclimatisation

 

[Bruce Leyland-Jones]

Adding onto @Colin_T 's advice, I'd also be curious about the parameters the fish were sitting in before you started your drip acclimatisation.

Personally, I'm still in two minds about the efficacy of drip acclimatisation, based on my following thoughts...
The fish are transported from their shop tank in a plastic bag and, for the duration of the journey, are sitting in their own waste.
Often this shouldn't be an issue, but for more active and/or stressed fish, this might be.
Assuming tank parameters are not too dissimilar from their tank of origin, I'd be inclined to remove them from their toxic waste asap.

My preferred method of transferring fish from bag to tank was/is to float the bag to equalise temperatures for half an hour and then to pour the bag through a net into a bucket. The fish then goes straight from the net to the tank. For the tank itself, I switch off the lights for about an hour, to give the fish a chance to find a hole to de-stress.

I was pleased to find that I was not alone in my thoughts;
KGTropicals and Acclimatisation

Another from KGTropicals:

 

[Bruce Leyland-Jones]

Another from KGTropicals:

Obviously, the second video is related to received shipped fish, as opposed to getting them from a local fish store.

 

[Bruce Leyland-Jones]

Rachel O'Leary doesn't even acclimatise for temperature!
See here.

 

[Byron]

For once the videos linked have accurate information, though one important fact has not been mentioned by any of the individuals. This involves the water parameter differences aside from temperature [I'll come back to this]. The reason for drip acclimation or similar water mixing in the bag or a bucket was promoted to be allowing the fish to acclimate to differing parameters. The fact is, this is impossible for fish in the space of hours, even days, even weeks. It can take several weeks and not all fish will successfully acclimate even then. So the individuals in these videos are correct in not wasting time over "acclimation" because it will not do anything beneficial. And as they all note, the ammonia issue is very serious and acclimation is not going to help there at all.

Temperature is debated among these individuals, and this is not surprising. Sudden temperature changes are very serious compared to gradual. But the degree of difference is part of this; a sudden change of 2 or 3 degrees will have much less effect (detrimentally) on most fish than would a sudden change of 10 degrees. Fish are generally better able to deal with upward changes in temperature than downward, so that is good as most times the bag water temperature will likely be below the tank temperature. But as I believe Rachel mentioned in one of the videos, temperature drives metabolism; thus temperature is the most significant factor in all of this "acclimation," and really the only factor with which we should be concerned.

 

[mark4785]

If you have been struggling to keep the nitrate level down this would suggest that you are doing infrequent water changes on the tank. Accompanying infrequent water changes is the issue of old tank syndrome whereby the KH and GH become depleted resulting in huge disparities between the tank water and any other water source such as your tap water or bagged water containing fish.

Also, which part of the tank did you obtain the water from that you used to drip acclimatise? If it was nearer the substrate you may have kicked up some sulphur which could have then entered the bag of water.

So with the above in mind I think the source of your problem is either:

1. Sulphur disturbance
2. Mixing old tank syndrome water with the bagged water too quickly and high nitrate toxicity.

Nitrate ultimately would have been ammonia and nitrite to begin with so double check that you are indeed registering 0 ppm for ammonia and nitrite with an in-date API Master Test Kit.