Urgent help


New Fish
May 26, 2011
I am new to this hobby, recently I got a gift of small 15-20L tank with 3 goldfish and 1 Black moor.
When I started looking at the net for fish care, I was terrified to learn that goldfish need larger tank!
I don't know what to do with the fish now, I don't want to kill them.
The fish are around 2 months old.
I am planning to buy a 4ft tank may be in 3-4 months. Can anyone tell me how much time I can keep those fish in the present tank? Your guidance are highly appreciated.
Ps:-Tank is fitted filter which is running 24hrs and oxygen pump, I am changing 20% of water everyday. Feeding twice daily. Until today fish seems to be alright.
They are swimming happily, no sign of stress or Sickness( some tips from internet).