if it's white and fluffy and sticks out of the body then you can use a fungal remedy from the petshop. Or if there are no catfish in the tank, you can try rock salt or marine salt. Use 1 heaped tablespoon per 20litres (5gallons) of tank water. Leave the salt in there for a week and then do small (10-15%) daily water changes to dilute it out.
Some chemical medications will affect the baby fish but if you use something like "Waterlife Myxazin" or "Triple Sulpha" they shouldn't cause any problems to the fish. You can also try natural products like Melafix & Pimafix. They are meant to help with minor infections and are safe for the baby fish as long as you don't overdose.
To work out the volume of water in the tank
measure Length x Width x Height in cm
divide by 1000
equals volume in litres
When measuring the height, measure from the top of the gravel to the top of the water level. If you have big rocks or driftwood in the tank, remove them before measuring the height.
Before you treat the tank do a 50% water change and complete gravel clean. This will reduce the gunk in the tank and allow the medication to work more effectively. It will also lower the pathogen count in the water and mean there are less nasties around to infect the fish.
Remove carbon from the filter before treating otherwise it will absorb the medication out of the water.
Make sure any new water is free of chlorine and has a similar temperature & PH to the tank.
