This fish has been swollen up for the past couple of months (I think its because it swallowed some gravel although I'm not sure) and I have over the past few weeks noticed a red growth on its body. Can anybody tell me what it is and if it is treatable.

I have uploaded some pics onto my twitter:

https://twitter.com/mikeroper91/status/251991266450104320

https://twitter.com/mikeroper91/status/251991518905249795

https://twitter.com/mikeroper91/status/251991612740222976

https://twitter.com/mikeroper91/status/251991703886655488

https://twitter.com/mikeroper91/status/251991796752719872

Please let me know if any of the links are not working or you cannot view the pictures!

Thanks for reading my question! :D