Red bellied Pacu sick?

[Slayer_will]

2 weeks ago I picked up 2 small red bellied pacu (one being an inch and the other 2 inches) and introduced them to my small 20 gallon community tank but just intill their big enough to go in my much larger predator tank (have place to put them and than when they out grow that have a pond, for everyone that's going to say why would I put them in a small tank). The bigger of the two developed a weird growth near his dorsal fin, doesn't look like ick to me and all the other fish in the tank are fine, just want to know what it is, if it needs to be treated, should I be concerned about the other fish in the tank

 

[Slayer_will]

 

[kno4te]

Looks like lymphocystis. Can add some salt, 1 tsp per gallon. Would monitor and quarantine (separate) the fish. It can be transferred to other tankamtes.

 

[Slayer_will]

Looks like lymphocystis. Can add some salt, 1 tsp per gallon. Would monitor and quarantine (separate) the fish. It can be transferred to other tankamtes.

What type of salt should I use?

 

[kno4te]

Aqaurium salt or any pickling salt will be fine.

 

[duanes]

I agree in looks like lymph.
Since Lymph is viral, there are really no effective meds.
I had some fish come down with it (it is ubiquitous like the common cold) after the stress of being shipped.
I did daily 50% water changes, and it was gone within a week.
And by the way, salt (NaCl) is salt.
When using it, I get either water softener, or rock salt.