CPD Thin And Strange Behavior

Indeed, it doesn't look good.

Sorry to hear the little CPD didn't make it.

Don't you quarantine new fish before adding to the main tank?

http://www.thinkfish.co.uk/article/isolation-hospital-or-quarantine-fishtanks-for-your-fish

I set up a 20L QT tank for about £40.

It's packed away dry when not needed and the filter sits in my main tank adding extra flow for plant nutrients until it's needed, so the bacteria remains healthy.

Strange indeed but good news nonetheless. Hope you can get him/her feeding? 

What sex is it BTW ?

I guess a poorly male could look like a female so I can understand why it would be difficult to sex.

Do you have a small tank you can set up as a quarantine tank?

I wonder if you could transfer sick CPD into a QT tank and add Liquifry No 1 to see if it might start eating infusoria to begin to build up an appetite for bigger things.

I know it sounds a bit odd but it must get hungry, perhaps it's just a case of trying to find something it will eat to get on the road to recovery.
I'm just thinking that maybe the fishy equivalent of baby food will kickstart something.

Sorry if it sounds like a stupid idea.

I do have an unused tank but it doesn't have a heater or filter, a combination of which will cost a lot more than this single fish. And as this isn't a particularly prized fish as it was always slightly weaker I don't think it would be worth the effort.

I understand completely.

Something to consider for the future:

http://www.amazon.co.uk/gp/product/B00CNVDMUE <- cheap 50w heater @ £7.95 + Free UK delivery
http://www.amazon.co.uk/gp/product/B00A4AZH3Q <- cheap micro filter @ £13.94 + Free UK delivery

These are the parts I use in my QT tank for quarantining new fish for a fortnight before introducing the new fish to the main tank.
Apart from that, it's ready to be set up as a hospital tank too if needed.

I just keep the micro filter running in the main tank permanently, in addition to the main filter, at the opposite end to aid water flow, so that it has a healthy bacterial colony in readiness for when I need it.

The rest of the kit, the tank, the heater, the half plant pot and the fake plants are stored dry until I need them.

Just a suggestion, as you already have a tank, an extra £22 will give you the quarantine tank / hospital tank that might come in handy in future.

So I ice+clove oiled it to make sure.

Just for future reference  in such a scenario, from what I've read, I think the ice is probably best left out. Hopefully the remainder of your CPDs will get on swimmingly, though. 

I wouldn't be surprised if a shop's supplier didn't know and made something up  But wild caught fish aren't immune from deformities, they are just less likely to be caused by inbreeding. There was just something about the photo of Barney's cpd that said to me developmental problems rather than sickness.