Black spot on abdomen of Harlequin rasbora

[Ryan_F]

Alright, last night, I would have taken a photo but it was like 3 am, I noticed one of my harlequin rasboras has a black spot on its abdomen kinda? It wasn’t a poop, it was ahead of the poop shoot, but it looked like this black spot maybe a cm or two ahead of the poop shoot, I thought it would be alright for like, 4 hours, but geez was i wrong, woke up at 7am, and it was dead in a plant, some of my other fish were eating it tail. Is this bad? I don’t think I need to medicate, but so I need to water change? All other fish seem healthy.


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[Colin_T]

Do a 75% water change and gravel clean the substrate each day for a week. this will dilute nutrients and disease organisms in the water and reduce the chance of the other fish becoming infection.
Make sure any new water is free of chlorine/ chloramine before it is added to the tank.

A lot of fish change colour at night and usually go darker or develop dark patches to help camouflage them. The dark spot might have been that.

The main reason fish get black patches on their bodies is from chemicals burns (overdosing with medication or chlorine/ chloramine in the water) or bruising where the fish has been physically injured.

Monitor the other fish and post pictures of any that look unwell.

 

[Ryan_F]

Ok, he was swimming around with his head up and his body down on an angle, with that brown/ black spot as I said, I will do that. I use stress coat, so that kills chlorine no new fish have been added so it might just be one of those things were a fish just dies, it was still purple even though he died, so he wasn’t stressed I don’t think


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[Colin_T]

If a fish is swimming on an angle with its head up and tail down, and the fish struggles to stay in the water column when it stops moving, then it usually has a swim bladder problem. Basically the fish can no longer remain buoyant in the water and constantly tries to swim up to its mates but sinks back down as soon as it stops swimming.

If that is the case there is nothing you can do for the fish.

Swim bladder issues are not that common and don't normally affect other fish in the tank. Although bacterial infections and genetic disorders can cause swim bladder problems and can occur in other fish if they are related or have picked up the same bacteria. However, this is quite rare and unlikely to be the case here.

Just water change, gravel clean and monitor them. If any more of them start swimming funny or changing colour, then post pictures and a short 20 second video of them asap.

 

[Ryan_F]

If a fish is swimming on an angle with its head up and tail down, and the fish struggles to stay in the water column when it stops moving, then it usually has a swim bladder problem. Basically the fish can no longer remain buoyant in the water and constantly tries to swim up to its mates but sinks back down as soon as it stops swimming.

If that is the case there is nothing you can do for the fish.

Swim bladder issues are not that common and don't normally affect other fish in the tank. Although bacterial infections and genetic disorders can cause swim bladder problems and can occur in other fish if they are related or have picked up the same bacteria. However, this is quite rare and unlikely to be the case here.

Just water change, gravel clean and monitor them. If any more of them start swimming funny or changing colour, then post pictures and a short 20 second video of them asap.

Usually of a night all of them are pale, I assume that’s normal as they have been asleep and I do a final head check before I go to sleep, as sad/mean as it sounds I’m happy that it sounds like it might be swim bladder, I did think that but the black spot concerned me, I have seen a lot of them poop and they look normal, so I assume that it’s ok, I’ll keep up with the water changes,


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