Green Spotted Puffer - Please Help!

[Anastacia]

pH - 7
Nitrates - <10
Hardness - unknown
Nitrite - 0
Ammonia -0
KH/Buffer - unknown
Water Temperature - 78*

Our GSP, Chompies, we've had for about 8 months now with no issues.  In brackish water.  Solitary tank.  Until today was eating well, super active.

We woke up to him being listless at the bottom of his tank, belly and face color are off and he seems like he's gasping. Upon closer inspection, his gill flaps have something coming out of them but I'm unsure if it's a parasite or a fungus.

<a href="https://ibb.co/gybSH5H"><img src="https://i.ibb.co/Y24cYzY/20201118-165941jpg" alt="20201118-165941" border="0"></a>

[Anastacia]

Added another picture from his other side.  It looks like a small white worm thing with a little black dot hanging out.  Im sorry it's kind of hard to see. 

[Preston John]

This sounds like anchor worm to me. I’ve never had it with any of puffers but I’m sure @Cory or someone else here will chime in. 

[Cory]

Seems odd that a parasite like that could survive the brackish water. What salinity are you running? My first thought would be to up it in an attempt to just kill it off. 

[Anastacia]

2 hours ago, Cory said:

Seems odd that a parasite like that could survive the brackish water. What salinity are you running? My first thought would be to up it in an attempt to just kill it off. 

Salinity was around 21, Spec Gravity at 1.106 according to the hydrometer.  It was a quick turn around.  Within 24 hours, our little guy, Chompies, was gone.

I initially thought it was anchorworms in his gills but didn't even get a chance to try to treat.

Thank you for the replies though!