Unexplainable Fish Deaths

[Jay Hemdal Verified Community Expert]

Tank at full light. Firefish was the only one that would come out. Damsel got spooked by the high light

We do hear this issue fairly often. Determining cause of death for a group of fish is difficult to do after-the-fact. The first thing you need to do is understand that the fish losses are probably not all related. People tend to lump all unknown fish deaths into one big group, but there are often multiple causes, especially when the losses are spread across an extended time frame.

Invertebrates doing fine? That almost ALWAYS rules out problems with the water.

Fish living for weeks after arrival? As you pointed out, that rules out any issues with acclimation.

Acute fish loss is usually easier to determine - all the fish dying in a week or two points to protozoan disease in almost every case.

With flukes, the losses will be extended over weeks to months and some fish may not be affected.

IMO - the clown gobies likely had issues with the way they were collected - they live deep in coral branches, so collectors use drugs to scare them out, and this causes latent mortality, weeks later. Personally, I won't buy these any longer.

One key symptom that I didn't hear you mention is respiration rate. Many home aquarists miss that important symptom, but it can be a very good indicator of certain diseases. Any fish breathing faster than about 100 gill beats per minute may have an issue.

Jay

 

[TMORGAN1980]

I’d say 50% of the fish with symptoms had rapid respiration. Are you thinking it’s could be flukes and only fallow will get rid of them

 

[Jay Hemdal Verified Community Expert]

I’d say 50% of the fish with symptoms had rapid respiration. Are you thinking it’s could be flukes and only fallow will get rid of them

Fallow or hyposalinity will break the life cycle of flukes. The fishless fallow period is only 35 days, but I go 45 for an added buffer.
Jay

 

[TMORGAN1980]

Sort of update on my original post. I added 2 homeless damsels to the tank almost 3 weeks ago. They are perfectly fine as are the 2 other remaining fish. If flukes or another parasite were present in the tank, how long would it take to re-emerge when new fish are introduced? Or could the original deaths have been something else? Or does whatever parasite I have not affect damsels/firefish?

 

[Jay Hemdal Verified Community Expert]

Sort of update on my original post. I added 2 homeless damsels to the tank almost 3 weeks ago. They are perfectly fine as are the 2 other remaining fish. If flukes or another parasite were present in the tank, how long would it take to re-emerge when new fish are introduced? Or could the original deaths have been something else? Or does whatever parasite I have not affect damsels/firefish?

Did you run any treatment? There are different species of flukes, some infect all fish, while others are more specific to certain species. Also, as I mentioned, flukes can take weeks/months to kill and in some cases, the fluke infection becomes chronic, and the fish can just live with it. Then, it may not have been flukes at all, but rather, something non-infectious specific to the fish that died.

Jay