own_highway_somerandonumbe

@Colu, thank you for the info, and the LFS Owner reached out on his day off to say pretty much the same thing (bless him) to confirm. Glad I joined. Was definitely on a not fun stress day today fearing the worst

Yeah, that's what I've been seeing and having trouble diagnosing if it was genetic vs illness. He's not swimming abnormally, and the other fish aren't shunning him like some do for sick fish....and I've not seen any ulcers, sores, weight loss or swelling as you mentioned. If it does end up mycobacterium, i assume those other symptoms would show up? And would the rest of the school get it first or would another fish start showing signs first? (I have pea puffers, dwarf gouramis, cherry barbs, guppies and a blue phantom pleco) Also I'm assuming if it is the mycobacterium, there's nothing I can really do to get it out of the tank right?

From what little I know, my LFS has told me plecos are slow growing fish and given their lifespans, could be years before they hit full size.

So I apparently have no concept of distance....I went down to look again, held a tape measure up to the glass and waited for him to get curious. He's just shy of 1.8"; which is still on the larger side....definitely possible. The largest threadfin in the tank is just over 2". Thanks for the input! Any hope it's not an illness is great. Hoping there's some more folks on here able to chime in with similar feedback; for now I guess I have to keep an eye on it.

I think he's full size, one of the biggest in the tank; I'd say about 2.5" without the tail. I don't know how big he was when I got the school. I don't think any of them were over an inch and a quarter, but I'm probably wrong. I thought they were both fast growers and could live up to 5 years?

What do you mean by old age? I don't know how fast threadfins age, but they shouldn't have been that old when I got them 4 months ago.....I also didn't know they got humpback when they get older. Both could be a huge relief for me, I've been spiraling all day (LFS is weirdly closed on Tues, haven't been able to get ahold of them to ask) thinking that it might be fish TB. I'm taking it with a grain of salt (no offense), but any possibility it's not an illness would be a huge load off. If it were fish TB; would you say a symptom would be a much more crooked back in one particular area? It does look like his spine curves back and forth from behind his head all the way to his tail......

Alright, trying here in addition to reddit: I have a fully grown male threadfin rainbow that's developed an odd body shape and I'm not sure if it's something they're genetically predisposed to; or if it's something malignant like fish TB. I grabbed a few photos, apologies on the quality, he wouldn't sit still. He is the only one who looks like this, but he's always had a higher/larger forehead than the other threadfins. If it's an illness, how do I quarantine a schooling fish without it stressing? If it's fish TB, is there anything I can do with the tank to head off other cases other than remove and euthanize this threadfin? I've had my 40gal cycled and with fish for 4 months, the threadfin school and my blue phantom pleco were the fish-in cyclers. Water parameters are in the photos. Temp is 75.5 F, and ammonia is close to 0