Fritz Maracyn

Maracyn® is a specially compounded broad-spectrum antibiotic which has been shown to be effective against a number of pathogenic bacteria associated with ornamental fish disease. It was developed for complete but gradual dissolution in water. It is primarily effective against gram-positive pathogenic organisms. 

Provides relief from bacterial infections such as body fungus, bacterial gill disease and popeye. Also helpful against mouth fungus, open lesions, hemorrhagic septicemia, and slime disease. Symptoms of possible bacterial infection can include clamped fins, swollen eyes, heavy or rapid breathing, patchy coloration, change in swimming behavior or corner-hiding. Consult a veterinarian or fish expert for assistance in diagnosis of disease causing organisms and treatment options.

All suspected bacterial infections should be treated immediately.

Active ingredient: Erythromycin


Directions & Dosage

Add the contents of one packet per 10 gallons of water and repeat every 24 hours for 5 days. Repeat this 5 day treatment only once if needed. 

Day 1: Add the contents of one packet per 10 gallons of water.
Day 2: Add one packet per 10 gallons of water.
Day 3: Add one packet per 10 gallons of water.
Day 4: Add one packet per 10 gallons of water.
Day 5: Add one packet per 10 gallons of water.
Day 6: Repeat this five-day treatment if symptoms improve, but have not completely disappeared. If no improvement has occurred, try our Maracyn® Two and/or Maracyn® Oxy treatments.

For best results, use Maracyn® in a quarantine tank
Remove carbon during treatment, maintain adequate water flow or aeration
Discontinue use of skimmer during treatment if foaming is a concern
UV Sterilizer can be used during treatment
Always complete a full course of treatment, even if symptoms improve or disappear before the fifth dose
No contraindications: can be used with all of our other products and meds
Safe for use with invertebrates
Some more sensitive plant species may display yellowing, but this condition generally improves after the treatment; remove any plants if concerned
Do not perform water changes during the course of treatment. Maracyn® does not inhibit nitrifying bacteria, and will not impact the biofilter. If ammonia or nitrite is a concern, detoxify during treatment with Fritz A.C.C.R. or Fritz Complete
Overdosed? Perform a large water change if distress is observed
Note: FOR AQUARIUM USE ONLY. Consult a veterinarian or fish expert for assistance in diagnosis of disease causing organisms and treatment options. If you are unsure of the specific infection, Maracyn® may be used concurrently with Coppersafe®, Maracyn® Two or Maracyn® Oxy.