What's the biggest red tail shark you've ever seen?

[Ogertron3000]

Here’s my big one, was around 12cms.
It was given to me for free from the LFS when they sold some fish I had a deposit on as an apology. I didn’t really want it but took him home, 3 years later he was this big and causing absolute mayhem in my tank so he ended up back at the shop.
I was sad to see him go but the casualty rate in my tank was too much. A bunch of swordtails were killed but the final straw was a very nice keyhole cichlid I had too.
For some reason my daughter called him Kevin.

 

[Fishman Dave]

I'm just curious to how you got your red tailed shark to be heavy bodied. I've kept a rainbow shark for a year now and he's 3-4 inches long but I've never figured out how to get him to get that thick body that you see online.

He/she eats a lot and clearly gets full (big belly) but he never gets fully thick bodied.

Do you (or anyone else) have any advice?

I think I would go with the concept they are similar to many other fish, such as clown loach. One sex being skinny and the other not so, but probably only starts being very apparent after a certain age.
Based on this there will be some fish, that no matter how old or how well fed, are not overly “solid bodied”. Hard to tell I suppose too since not usually a fish kept in groups.
I have the same thoughts with my black shark (not red tailed) and am growing more on to try keeping numerous in group in my pond. Should have started with RTBS (5”) I guess, as if in my experiment they fight constantly, it will be much harder to rehome them at >24” each.

 

[Morti]

It's the females that become deeper bodied when mature according to seriously fish.

Ours was a really pain when it matured as it developed a taste for fish slime coats and it would relentlessly rasp at the bodies of our dorms, to the point they caused a bacterial infection (thankfully not fatal). I think they are wonderful fish if you don't have other grazers or sedimentary species and instead have chunky fish that can handle themselves.