Who knows what this bump on Golden Sailfin is?

100g Tank
4 Adults and 15 fry
NH3 0
Nitrates 20 to 30
Temp: 78F
Hardness 300+
WC q 3-4 days, 50%
Partially planted
PH: 7.8

Hey everyone and thanks in advance. I have a 2-year-old Female Golden Sailfin about 4 inches long, has had several batches of fry, and has always been healthy. About 7 weeks ago, she was swimming nose down, aborted all her fry, (in various stages of development), and stopped eating. QT tank with Maracyn 2 round, then paracleanse round. then ICH-X. After 5 weeks, she was swimming normal again ( a little shaky), eating good, and back to her very friendly self. But, she had started to develop "fuzz" on her right side growing from a bump. (See Picture). I did not want to do any more meds so I did Five tbsps. salt in 10g tank for a week, the bump and fuzz went away. Instead of putting her back in the 100g tank, I have her in a 30g with pristine water so I can watch her and keep her away from males. After 2 or 3 days, the bump appears to be back.
I hate to put her back in the QT but I will if I have to. She's been thru so much. What is it? Injury? Not a tumor, cause it was eradicated by medication. Maybe a scrap with a cory? Maybe my bully male hurt her? He is aggressive. Any thoughts? Thanks!!
Deb

 

Looking kinda like a pimple like that,makes me think possible cyst

 

Hey BigManAquatics, thanks for responding. I didn't think of that... does resemble a cyst. Is there any treatment for that?

 

It does look like a cyst or abscess. Clean water is the treatment once it pops, as long as it drains completely (this is not an invitation to pop it, please don’t pop it) and doesn’t get infected it should heal up fine.

 

Oh that is so hopeful! Thank you for your help. I moved her to the 30g and she loves it. She's kinda big for it, but she shares it with some leopard platys. I will keep an eye on it for sure. And NO popping, promise. Have a great night!!
Deb