What is this reoccurring growth?

[secuono]

Have you tested your water?

Yes

If I did not test my water...

1. ...I recognize that I will likely be asked to do a test, and that water tests are critical for solving freshwater health problems.

Do you do water changes?

Yes

If I do not change my water...

1. ...I recognize that I will likely be recommended to do a water change, and water changes are critical for preventing future freshwater health problems.

12in long, a few years old. Eats great, day or night, frozen, dried and a few accidental live fish...Heavily planted tank, almost no tankmates, all safe. About 40% w/c weekly, well water, no chemicals needed/used. No ferts used.

Hopefully, pictures will load in order. Dates added just in case.

First noticed in mid July. Started to do larger water changes. Blew, healed. Went back to 40% w/c. Seemed to be gone. Then I just noticed it growing again the other day.

Any ideas what this is, possible treatment?

 

[danotaylor]

I'm no expert but it looks like a ruptured cyst. Are ghost knives supposed to be that thick? It looks overweight but the July 27th pics appears to show some irregularities in its abdominal contours. I wonder if it has other more concealed cysts as well and the jaw cyst is more pronounced since there is bone immediately underneath it
As far as treatment goes I'd assess the fat content % of the foods it's getting & keep that to a minimum, keep the water super clean, and dose salt at 1tbsp/5gal to reduce bacterial counts & the possibility of secondary infection.

 

[secuono]

It's a glutton. Can't really stop it eating everyone else's food. Only thing it doesn't like is raw cucumber. It eats the pest snails in the tank, too.
Googling cysts, if it's Lymphocystis, it'll never go away permanently and nothing to be done about it.
It has since disappeared again.