What size pack do I need for my filter?

Usually you would use Hydor LAB Zeolite to absorb ammonia in the water. Its best to use the product in a filter bag and the bag put into the aquarium close to the flow. Hydor recommend checking Ammonia levels and changing the Zeolite if the levels are not reducing. Once Ammonia levels are back to normal the Zeolite should be removed and thrown away.