are you also doing daily water changes to keep the ammonia and nitrite levels at zero?
i personally wouldn't use any chemicals other than a good dechlorinator, do daily testing for ammonia and nitrites for the first week or two, and whenever you have any amount, even if it seems miniscule, change out the water until those levels are back at zero. number one killer of new fish in a new tank that isn't cycled is ammonia and nitrite poisoning. after the first couple of weeks start testing for nitrates too, to see how the cycle is progressing, and keep up those water changes to keep ammonia and nitrites at zero.
so no fishkeeper friends near by that have some healthy and established filter media you could steal? that would be the best option in this situation.