Fritz Maracyn

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  • Treats bacterial infections
  • Safe for aquarium plants
  • Safe for shrimp, snails, and other invertebrates

Fritz Mardel Maracyn® is a specially compounded broad-spectrum antibiotic (erythromycin) 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. Symptoms of clamped fins, swollen eyes, heavy or rapid breathing, patchy coloration, change in swimming behavior or corner-hiding can be signs of possible bacterial infection.

The savings come in the 24-count package or larger over the traditional API Erythromycin. Each packet treats 10 gallons. The 60-gram bulk container treats 1,000 gallons. We recommend using an air stone in the aquarium when treating with Maracyn.

Customer Reviews

Based on 424 reviews
Jordan (Hilliard, OH, US)
Columnaris cured, snails and plants are safe

Case of Columnaris was slowly killing fish (aka saddleback - patches on skin, lethargy, then death). Have shrimp and snails in tank too, with fish. Used for 1 cycle. Only lost 1 more fish during treatment, but they were in bad shape to begin. Everyone else seems all good. On day 4, the vibrancy and energy returned to the tank. The first 3 days was a lot of laying around. A lot. Used a bubbler to try to add more oxygenation. Shrimp and plants are looking good too. Sooo happy with this product

MaryJo P.

This stuff is awesome.. it's way cheaper here at aquarium co-op then to buy it anywhere else that i've come across anyways .. just awesome products at a great aquarium store..

Jeanie (Romance, AR, US)
Fritz Maracyn

I won't know if this worked for a few days. Just put a few platys in my tank and hopefully whatever was in there killing my fish is gone.

Alexis T. (Snohomish, WA, US)

Fritz Maracyn

Ian C. (Jonesville, MI, US)
Life Saver!

Something was going seriously wrong in my African cichlid tank. Fish would stop eating, and then drop dead. Water parameters always came back good. I started to suspect that there was some sort of bacterial infection, so I gave Maracyn a try, and it did the trick. The plague ended!