Fritz Maracyn®

Maracyn is a broad-spectrum antibiotic (erythromycin) that dissolves gradually in water, primarily effective against gram-positive bacteria. Treats body fungus, bacterial gill disease, popeye, mouth fungus, open lesions, hemorrhagic septicemia, and slime disease. Safe for fresh and saltwater systems.

Dosing (per 10 gallons)

• Days 1-5: 1 packet each day
• Day 6: repeat the 5-day course if symptoms have improved but not fully resolved; if there's been no improvement, switch to Maracyn Two or Maracyn Oxy instead

Important notes

• Best used in a quarantine tank; remove carbon during treatment and maintain flow/aeration
• Pause the skimmer if excess foaming is a concern; a UV sterilizer can stay on
• Do not perform water changes mid-course; watch ammonia/nitrite (Fritz A.C.C.R. or Fritz Complete can help if needed)
• Always complete the full 5-day course even if symptoms clear early
• Safe with invertebrates; sensitive plants may yellow temporarily
• For aquarium use only - consult a vet or fish health expert for diagnosis

Sizes: 10-count treats 100 gal (item 46001), 20-count treats 200 gal (item 46002), 100g jar treats 1,000 gal (item 46046), 400g jar treats 4,700 gal (item 46051).

At Marine Concept Supply, all sales are final. Due to the sensitive nature of live animals and aquatic products, we do not accept returns or exchanges under any circumstances. Please review your order carefully before completing your purchase. No Cancellations.

If you have any questions or concerns about your order, please contact us at shop@marineconceptsupply.com and we’ll do our best to assist you.

We Ship UPS and will send tracking as soon as the item ships. 

Return shipping for any approved warranties are not covered and will be subtracted from the approved credit total.

Restock Fees apply to some products, due to their size or a manufacturer policy.Each product with a restock charge is marked online, in the description.

Please inspect your order upon reception and contact us immediately if the item is defective, damaged or if you receive the wrong item, so that we can evaluate the issue and make it right