What is your ammonia reading? Sounds like your tank is recycling for some
reason, probably something has killed off the bacteria. Best to use water
changes rather than chemicals as chemical often prolong the cycling process.
I presume your vacuuming the gravel? You are treating the water before you
put it in at water changes? Chlorine will kill your bacteria.
Large (50-89%) water changes twice a day are needed to get the ammonia down
as it's highly toxic, cut back feeding to half the amount and only every 2
or 3 days. You also need to be testing for nitrites. Only when you're
getting zero reading for both are you and your fish home and dry.
Your nitrites are likely to go up so keep an eye on them. Do you have
another mature tank you could swap the filter over with?
What size fish do you have in there? And how many?
Jim Rojas
push sopme pennies in the gravel aroudn them. It sure makes them get a
boost and take off. Its also good for the fish health too.