Luckily the 'sifu' has come in before its too late.
Don't know where I get the number 3% concentration for half hour treatment.
Must have mixed up with all the number and decimal point.
Just another question Andrew.
I have been putting about 200 gram of coarse salt into the discus tank of 200 litre ( top up 100 gram on daily 50% water change ) contineously for the last couple of months.
What is your opinion of this practice?

One side of tank ( 6 inches ) has been partitioned off as boilogical filter and sponge pre filter ( washed daily ).
Water pump (filter) rate about 15 litre per minutes.
2 air line.
18 pieces of average 4 inches discus in the 4 ft. tank
5 feeding per day, 2 times beef heart, 2 times tetrabits and 1 time frozen red worm.
PH about 6.6 ( using phosphorice acid )
Ammonium test kits shows 5 ppm total ammonium
I was hoping the salt will help prevent the fish from nitrite poisoning.

Your advise much appreciated.

Cheers!

BT Lee