Poorly Danios

[scouse_andy]

I had 5 healthy Danio in my cycled tank for a couple of months, all in good health. Water tests have always been fine and I do the weekly water change.

About two weeks ago one of them suddenly died having presented no symptoms beforehand. I found him underneath a plastic decoration and assumed at the time that he had got stuck.

Since then, two more of them died, in the hours before they died they looked very lethargic. One was gasping for breath and had a chunk of flesh dropping down from below his jaw, the other had a slice taken out of it's back.

At this point, I assumed that maybe they were getting a bit aggressive as there were so few of them so I bought six more, bringing the total to 8. Since then another of the original two has died, she was very lethargic and had a red sore on her side like she was bleeding.

The last of my original five danio has this morning developed a slice across his back and is looking lethargic too. I have no idea what is causing this and they don't appear to be fighting. I have a female who looks ready to spawn any day now. I looked up about diseases and the only one really mentioned with Danio was velvet but the symptoms don't seem to fit.

Can anybody offer me any advice at all. I am really keen to save the rest of these little fellas and get to the bottom of the problem.

Thanks in advance, Andy.

 

[Miss Wiggle]

Hi Andy, that sounds strange, can you give us some more info on the tank and hopefull we can help you out, please answer the following questions

1. Water parameters. (ammonia, nitrate, nitrite, PH, temp', Hardness etc)
2. A full description of the fishes symptoms.
3. How often you do water changes and how much.
4. Any chemicals and treatments you add to the water.
5. What tank mates are in the tank.
6. Tank size.
7. Finally Have you recently added any new fish?

 

[scouse_andy]

Ammonia and nitrite are at 0. Nitrates are at about 40. Temp is at 24 C. pH is 7.4.

Symptoms are general lethargy of the affected fish - floating in one place, not feeding much, occasionally swimming with the others (the rest are fine). The affected fish seem to have slices out of their back or side or in the case of the first one under the jaw.

I do 25 per cent changes once a week and always dechlorinate with stress coat.

No chemicals or treatments added.

I only have these Danio in the tank, all I have done is added 6 more to the remaining 2 of my original batch.

The tank is a 30 litre Biorb, normally I wouldn't stock it so high but I am fishless cycling a new 240 litre tank and these fish will be going in there as they grow bigger once it has cycled.

Any advice welcome.

Thanks for your help Miss Wiggle.

 

[Miss Wiggle]

hmmm the tank's overstocked and too small for danio's really as you seem to be aware.

the two problems i would predict are that the filtration wouldn't cope but the good test results would disprove that, keep testing your ammonia and ntirite especially though to check for problems. the second and most likely is that the small space would be stressful for the danio's and stress can bring on diseases or illness's. I can't say i recognise those symptoms as any particular disease but that's my best guess for a reason why they've got poorly.