Pictus cats are not a good fish to start a tank off with, all members of the Pimelodidae family are intollerent of nitrogen pollution and will quickly fall ill and die if exposed to ammonia and nitrite for extended periods. The best thing you could do is return the pictus cats back to the store where they were purchased and either buy some small hardy fish such as danios to cycle the tank or do a fishless cycle using ammonia to start the tank. Catfish from the Pimelodidae family should not be added until the tank has been set up for at least 6 months.
If you cannot return the pictus cats you will have to attempt to keep them alive with daily and maybe twice daily partial water changes (10-20%) until the ammonia and nitrite levels have subsided and the nitrates are rising steadily, do not feed the fish during the cycle as this will just cause the cycle to run out of control, fish excrete ammonia just by breathing. You will need to purchase a test kit with individual tests for AMMONIA, NITRITE and NITRATE to moniter these levels so you know where in the cycle you are.