Aquarium Activated Carbon Calculator

For general maintenance: ~1.2 g per gallon (about 1/4 cup per 20 gallons). For medication removal: 3 g per gallon (3× maintenance dose). For tannin removal from driftwood: 2.2 g per gallon. Saltwater and reef tanks need 20% more due to higher organic loading. Replace within the schedule — exhausted carbon stops adsorbing and can leak absorbed compounds back.

Maintenance use: every 3-4 weeks. After medication treatment: within 72 hours of starting carbon to prevent re-release. Tannin/odor removal: every 2 weeks (saturates fast). Premium carbon brands (Seachem MatrixCarbon, Marineland Black Diamond) last 25-30% longer than budget brands.

No. Carbon adsorbs fertilizers including iron, manganese, and some trace elements plants need. Use carbon only when you need to remove medication, tannins, or unusual odors. Most planted tank keepers run carbon only 1-2x per year for targeted removal, not continuously.

Activated carbon adsorbs medications, tannins, and some organics. Purigen (Seachem) is a synthetic resin that adsorbs a broader range of organics including nitrogenous waste, leaving trace elements intact. Purigen is regenerable (bleach + Prime rinse); carbon is single-use. Many keepers run Purigen as their default and add carbon only when needed.

No. Activated carbon does NOT remove ammonia or nitrite — that's the job of your biological filter (bacterial colonies). If your tank has high ammonia, you need a water change and a cycled filter, not more carbon. Common beginner mistake: running carbon continuously and skipping the nitrogen cycle.

Yes. Carbon adsorbs iron, manganese, copper, and some other metals/nutrients. In a planted or reef tank, continuous carbon use can cause deficiencies. Dose trace elements 24h AFTER removing carbon if you've been running it. For reef tanks, many keepers run carbon only passively in a media reactor, not in the main flow path.