Help! Sluggish fish lying on filter

Help please. My swordtail is lying on the filter, very sluggish and looks like dying.

Filter working, lots of bubbles. Pearling on (plastic) leaves in 13L tank.

Dolphin F800 filter.
1 swordtail, 2 plattys, 2 ottos.

Been going 5 months.
Doing bi-weekly 20% water changes.
I don't overfeed.

TDS 218
pH 7.9

The other fish are perfect.

I will post a pic of swordtail at top, and rest of fish happy and tank showing air filtration bubbles.

 

I just did an emergency 40% water change. The swordtail is barely moving. As the water level dropped she lay on the filter and then slipped off.

 

Sigh.
She temporarily gave me false hope by leaving her place on the filter, but now settled on the bottom of the tank, kind of on her side.

I presume this is the end.

Losing fish sucks.

 

Nothing external that you can see? Cos if the other fish are fine, maybe it got hurt or its internal and then that could spread

 

I had a look. I don't see any injuries. She has swum up into a little slit behind the filter, and seems intent to die there. I removed her but she returned.

 

So sorry, to be able to help i think everyone will say get all the parameters of the water tested to know if it's maybe that and if there's any physical signs of injury or disease to

 

I can see one male platy, not too sure about the other one. She, swordtail might have been harrassed by the male/s platy and might just be hiding. Have there been a lot of chasing going on?

 

Hi @Ness
Sorry to hear, hope she makes it

There could be various reasons
When testing water, the most important readings are Ammonia, Nitrite and Nitrate... not sure what yours are so difficult to tell

It could be she was bullied... could be she is older than you think..
Good luck, hope she makes it

 

Hi Reedfish. Yes, I am actually looking for a second-hand tank. This little tank has been a very hard learning curve.

 

Hi MariaS. From what I've read, I think it's nitrites. We had a power outage the day before, so the filter wasn't running for 12 hours. I think that pushed the nitrite levels up.
My swordtail didn't make it.

And even though I did 40% water changes for the next 3 days, one of the plattys jumped out and died as well. Managed to squeeze himself through a minute hole cut out of the lid for the wiring of the light. Must have been pretty committed to succeed...

 

Thanks A New Day.

You see, I have this old inside fireplace without a job, and hubby is pushing to utilize it for a bigger tank.

I am feeling slightly overwhelmed bybthe logistica though ...

I will start a new thread specifically regarding this. I need all the advice and inspiration anyone can spare!!