GAC

Definition

GAC (Granular Activated Carbon) is an adsorptive filtration media that removes dissolved organics, tannins, medications, and yellow water tint from aquarium water.

Practical use in aquariums

Run continuously in a media reactor or canister filter chamber. Replace every 2-4 weeks. Carbon depletes faster in high-bioload tanks. Bypass GAC during medication treatment - it strips the medication.

How GAC fits the bigger picture

Understanding GAC matters because it's connected to broader husbandry decisions: equipment selection compounds: skimper + return + dosing all need to match each other and the tank size.

Browse the Fast Aquatics care library for full husbandry tutorials covering GAC in context.