Tag went from fat to deathly skinny overnight. How?

[Perpetual Novice]

I woke up this morning and found all of my fish breathing heavy. Especially my blonde naso. I found my bubble tip anemone had finally died and poisoned the tank so I transferred the gasping fish to my observation tank and did a massive water change. The other fish all worked up fine but the naso did not.

I would figure it was just the most affected by the toxic water it was forced to breathe overnight. But what I noticed was how skinny it is now. It looks like it hasn’t eaten in a month. Skinnier than I ever thought it could be. And last night it was very plump and eating heartily. It’s night and day. Like the difference between a fresh tube of toothpaste and a spent one.

How did this happen. Could there be something other than an ammonia spike going on here?

 

[Mjrenz]

I woke up this morning and found all of my fish breathing heavy. Especially my blonde naso. I found my bubble tip anemone had finally died and poisoned the tank so I transferred the gasping fish to my observation tank and did a massive water change. The other fish all worked up fine but the naso did not.

I would figure it was just the most affected by the toxic water it was forced to breathe overnight. But what I noticed was how skinny it is now. It looks like it hasn’t eaten in a month. Skinnier than I ever thought it could be. And last night it was very plump and eating heartily. It’s night and day. Like the difference between a fresh tube of toothpaste and a spent one.

How did this happen. Could there be something other than an ammonia spike going on here?

I'm not sure about the rapid weight loss, how does his breathing look now? @4FordFamily @HotRocks @ngoodermuth @Big G

 

[4FordFamily]

I’m guessing internal parasites and it passed several. This is uncommon for it to be so drastic. Sorry for the trouble. Is the fish still eating?

Have you ever noticed white, stringy poop?