Actually , Prime does lock ammonia.. it locks H ion to NH3 turning it into NH4 a less toxic ammonia.
(loose definition of lock)
water changes are probably one of the most important maintenance factors in fish keeping.
while in the past it was acceptable to do water changes once ot twice a month..
over time it was discovered that TDS increases and can the simplest way to eliminate this was thru water changes.
how often and how much often depends on stock and stock quantities.
you can get by with as little as 10% per week if you have low stock quantities and the stock is tolerant.
in some cases when raising fry you will need to do at least 10% daily to maintain high water quality.
some fish like discus usually benefit with larger and frequent water changes 25-50% 2-3 X weekly.
as you know pH is largely not a factor in the health of the fish. gh btw is a measure of the general hardness and help to determine if you have hard or soft water. which can have an effect on the fish. fish may be sensitive to metals in the water. pH in this case can make these metals more soluble to the fish and more detrmental if you have say acidic water.
Again these are varialbes which may or may not affect your fish.. part again due to the fishes sensitivity to these.
when getting new fish froma fish store.. you may have just gottne poor stock.
I cannot tell you how many tetras and tiger barbs dies for not apparent reason.
in water tha can sustain more sensitive fish like Discus.
all in all it may have been a factor you did not contribute too.
my suggestion.. try a different place for your stock.
I second all the votes for Prime being the best water conditioner.
