Photo of fish but not sure what is wrong?

[sidgolding]

Can anyone help me??? What is wrong with this danio????

 

[Brookster123]

Saddle rash could be columnaris.. tell us all about the tank.. more details the better we can help

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[sidgolding]

It is a very little tank 19 litres. Has 6 danio's in it. The tank is not heated and has no light but have a very high spec filter for the size of the tank. The tank has been running about 6-7 months and this is the first problem I have ever had keeping fish. Never had illness or anything before... Anything else you need to know? There is a snail in with the fish...

 

[sidgolding]

Also I have just got a new aquarium grass for the tank 3-4 days ago... She seems happy enough but it's looks like a massive love bite ( hickey ) or she has had a trauma?

 

[Brookster123]

Well the tank is def a bit crowded.. do you test your water? How often and how much water you change?

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[sidgolding]

I have always kept danios like this. I do pwc once a week of between 25/50%. All the reading in the tank are spot on. PH is perfect. I'm wondering if the snail could of done it? Or there is a disease caught of the new plant?

 

[sidgolding]

What ever it is appears to healing....

 

[sidgolding]

This fish is now happy as ever. Fully healed. And thinking about it she may have had a heart attack or a bleed, but she is fine now. Danio's have a great ability to heal as I'm sure most of you know.