Betta got attacked

[Ailill]

My crowntail betta got attacked by his tank mate, a pictus catfish. This is my first betta, so I'm clueless as to how to nurse him back to health. Or in fact, if it's possible for him to fully recover from this attack.
He's been hiding all day, otherwise I'd include a picture. I'll try to get one though, if anyone thinks it'll help figure out how I can help him...

Housing
What size is your tank? 3 gallons
What temperature is your tank? approximately 78
Does your tank have a filter? Not at the moment
Does your tank have an air stone or other type of aeration? It has an air stone
Is your tank heated? yes
What tank mates does your betta fish live with? a pictus catfish

Food
What type of food do you feed your betta fish? Hikari bio gold betta pellets and Tetra freeze dried bloodworms
How often do you feed your betta fish? 3 pellets once a day. Bloodworms once or twice a week.

Maintenance
How often do you perform a water change? A full change once a week, a 30% water change between full changes
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change? Tetra BettaSafe water conditioner


Water Parameters:
Have you tested your water? If so, what are the following parameters?

Ammonia: N/A
Nitrite: N/A
Nitrate: N/A
pH: N/A
Hardness: N/A
Alkalinity: N/A

Symptoms and Treatment
How has your betta fish's appearance changed? His tail and fins are shredded looking...
How has your betta fish's behavior changed? When I first noticed something was wrong he was floating at the top of the tank, not really moving. After being removed from the tank he's started swimming around again, but he seems to prefer hiding under the edge of the heater. He also didn't come up to the top of the bowl he's now in for his food. He waited until it sank to the bottom to eat.
When did you start noticing the symptoms? At about 3 am, this morning.
Have you started treating your fish? If so, how? I've not done anything yet. I don't really know what to do...
Does your fish have any history of being ill? Not ill, per say. he was poorly cared for before I got him. He's a crowntail, but lacked the spikes on his tail and fins, and the bowl he'd been in was disgustingly dirty. In the 2 months that I've had him they were starting to come back.
How old is your fish (approximately)? About 10 months

[Malvolti]

I'm hoping the hospital tank he's in is the 3 gallon, Pictus generally need much larger tanks in the 30+ gallon area and prefer being in groups. If they are both in the 3 gallon it could explain the attack. The pictus might feel crowded and doesn't want to share, they can get very agressive especially when cramped. They also tend to get very large and will eat anything smaller.

Anyways the best thing for the betta is to be put in a seperate tank from the catfish (which it looks like you did), to have daily water changes and a teaspoon of aquarium salt per gallon of water for a maximum of 10 days.

[Ailill]

The betta isn't in the 3 gallon tank at the moment. As it was 3 am when I saw the problem, and it being christmas today, I didn't really have the time to catch the pictus and clean the tank for the betta. That's going to be done first thing in the morning though.