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 423 reviews
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!

Ryne T. (New Britain, CT, US)
Big 3!

It’s part of the big 3, what’s not to love? I used as Cory advised in his live bearer disease video, saved my new Dalmatian sailfin Molly