Carbon adsorbs (damn you Byron, absorbs sounds bettera) chemicals and heavy metals until it is full. There's no way of telling if it's full or still doing its job.
If the carbon has been in your tank for 9 months then it's probably full and not going to adsorb anything. Take the carbon out and throw it away and do not replace it.
Assume today's treatment didn't work, do a 75% water change tomorrow, and start the full course of treatment next week. I'm not sure what the directions are on the pack but follow them.
If the carbon has been in your tank for 9 months then it's probably full and not going to adsorb anything. Take the carbon out and throw it away and do not replace it.
Assume today's treatment didn't work, do a 75% water change tomorrow, and start the full course of treatment next week. I'm not sure what the directions are on the pack but follow them.