The Puffer Forum

Ammonia and Nitrate 0 PH about 7.0
Salinity 1.007
The tank has been set up for about 2 years.
There are no live plants, all fake... have tried several different live species that supposedly highly resistant to salt, but to no avail... gave up on that a year and a half ago lol.
There is a figure 8 puffer that has been in there for a while and I added a brackish water eel to the tank about 8 months ago, unsure the exact species, the pet store had it labeled as marble eel, however nothing that i have ever looked up looks like this eel... so like I said unsure of actual species.
It is a 20g tank
The puffer is about 2 inches long and has been in the tank about a year and 6 months or so.
He has been feed jumbo krill for as long as I have had him as well as an occasional bloodworm or 2 here and there and sometimes snails.
A little over a year ago (maybe 2 or 3 months after I got him) the puffer developed a very bad external infection that took over a month to get rid of. He healed, but some scaring on his body still remains to this day. After he recovered, he was never 100% himself again as far as his personality. He remained highly timid for a few months before regaining most of his socialness and getting to the point where he could be hand fed again if you wanted to.

About a month ago he started getting real shy and his appetite lessened quite a bit.
Now, as of about a week ago he has taken to sitting at the bottom right corner of the tank almost laying on the sand.
I try to get food to sink down there for him to eat but he doesn't really mess with it much he did eat a bloodworm last night though.
His beak seems fine as far as size for him to be able to open and close his mouth.
I do however see what looks like a bulge around the top left side of his body about halfway between the tail and his fin that reminds me a bit of a tumor.

Are there any recommendations of what I can do? Could he truly have a tumor?

Welcome!
NO nitrate? Or si that nitrite?
pH should be around 8. What substrate are you using?
SG is best kept at 1.003-5.

A diet of krill isn't good at all. It's high in thiaminase & can cause lockjaw in puffers. They need a varied diet. library/feeding/feeding-your-puffers/

Yes, fish do get tumors. Can you post a pic?

I coaxed it into 1 of those little isolation boxes you can use to move fish between tanks and treat and such to try to get the best angle of picture to show bulge I am meaning. Hopefully you can still see pretty well with all the cropping I had to do to make it fit the 256 kb requirement.
You will definitely be able to see the scaring on it's skin... the white patches. Has been like that ever since that horrible infection it got that I had mentioned.

I apologize, yes I had meant Nitrites
I will work on lowering salinity a tad and upping PH a tad, I had been going by what I had read about them online when googling.
And I will look at getting some different foods now, on that I was going by what the pet store said was good.

On substrate, it might sound strange but I am using pool sand. Have it in 4 other tanks. It is more coarse so if it is messed with, it doesn't get kicked up and go into the filter since it doesn't mix with the water. An older guy that I got 1 of my tanks from swears by it. He builds and repairs tanks and has a good 20 or so that he himself has fish in. Told me he just goes to a local pool store and asks them for any 50lb bags they have that have holes and pays $5 for them.

Aragonite sand is recommended for substrate, as it buffers the water around a steady level of 8.
Try adding Melafix to help with healing/scarring.

What about that bulge on it's side that seems to be growing?

I'm not really sure but that's a GSP, not an F8. The bulge never goes down?

Yes, the bulge stays.
Also it looks like it hinders tail movement.
For instance, when swimming the tail doesn't really bend that direction much aside from the very end.
It is more like the tail right, straight, right, straight. and in resting position it is slightly bent to the right.

It really reminds me of the tumor that my little brother's cat has had for... several months now. It is hard to believe that she is still going as well as she is... it is more than twice the size of her head now. But she still walks and eats. Though she has to have special pills to keep food down.
And I of course meant cat (feline) not cat as in catfish.

What did the vet say about the kitty's tumor? Non-operable? Might be the same thing with your puffer.

They said there was nothing that they could do.
Said to try to keep her comfortable and prescribed this medicine to help her keep food down.
They gave her a few weeks to live, yet she has been going still for about 4 months.
She keeps fighting, she wants to live.

Did you ever get a resolution on this? The same exact thing is happening to my puffer right now!