Very sick Fire bellied Newt

Question
Hi..A friend bought my son 2 Fire bellied Newts from a shop about a week ago..one is fine..but the other one has not moved much since we got them and has now almost stopped moving at all, he is also very thin and will not eat.
The temp in the tank is 20c and i am feeding them live daphnia and live bloodworm, although for the first few days whilst my friend had them they had frozen bloodworm as this is what the shop advised so I am not sure if they ate at all as they will not eat frozen food for me.
I took the sick one to the vet yesterday who gave him some antibiotics...and he did pick up a little last night and this morning..he was moving about a bit more, however I have still not seen him eat and he has not moved for a while again.
I have to take him back to the vet in a week but I do not think he will last that long and I was wondering if you have any advice at all on what I could possibly do to help him (or her?)
What other foods can I try?..should I put fresh water salt in to condition the water?..I am a bit stumped as the advice I found on the Internet is sometimes contradicting..and the shop where I bought them (in the UK)..don't seem to know anything about them (they said to fill the tank with tap water and give them frozen blood worm and they will be fine?)

Any advice would be greatly appreciated
Kind Regards
Vicky

Answer
I would first of all increase temperature to 21 C and this should perk it up as it sounds to me like its too cold.  Reptiles and amphibians that are too cold will not eat.  The foods sound fine.  Did the vet tell you what the antibiotics were treating? Also are they wild caught or captive bred? The water should be treated for dechlorination and not salted as this really doesn't do much but soften the water in my opinion.  I would ask how the shop has theirs set up and mimic the environment.  Also are you using a filter of any kind? Also the website http://www.caudata.org/ is a good resource.