
Hi Sabby, WELCOME to FISHLORE, hope we can help.
First I am not familiar with "ammonia sack" that might be added to a filter, but if it were me I would SACK that right now! If you are having ammonia problems, lots of water changes will help. Do you use water that needs conditioning to remove the chlorine?
I always ask because I am on a well with no chlorine, and don't have to use it. Also make very sure the water you are putting back in is the same temperature as your tank water.
Even if you don't have anything to put in your filter overnight, get that out now. The reason is, because sometimes material that says it absorbs ammonia, will do just that until it gets full, then it will release it, and poison your fish.
How long has your tank been running? DID you cycle the tank before adding fish?
The MOST important thing, do you test your water. Water changes without knowing what your water parameters are, is a start, but you have no way to know how effective you are unless you test. SO we recommend an API Master test kit, DON'T rely on test strips........then let us know what the results of the tests are.
Ammonia:
Nitrite:
Nitrate:
When you change water every week are you vacuuming the substrate?
So, tonight, after you remove that filter material, change 50 % of the water. Then do another 50% tomorrow. Test your water, and let us know...... Hope this helps. Sorry your fish have been dieing.
Merry Christmas
