hi NZLASS first thing when disposing of fish it must be done humanely put 10 drops of clove oil in a dish and put the fish in it dies within seconds. Never freeze its very cruel . AS for the rest you seem to be doing everything to fast first of all let your tank mature for 4 to 5 wks a slow process add bacteria to the tank twice a week STRESS ZYME or INTERPET FILTER START i presume you have this in NZ I myself never use carbon filter pads when using medication they take it out of the water.only add a couple of fish at a time remember this is a SLOW PROCESS I hope this will help GOOD LUCK let me know how you get on and remember DONT overfeed