Fritz Maracyn

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

Fritz 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.

For the 10-count and 20-count boxes of Maracyn, the medication comes in individual packets where each packet treats 10 gallons of water. The 100-gram bulk container treats a total of 1,000 gallons of water and comes with a scoop for easy dosing. When treating with Maracyn, we recommend using an air stone in the aquarium, which may temporarily cause excessive foaming at the water surface.

Customer Reviews

Based on 559 reviews
kona a. (Kailua-Kona, HI, US)
One of my favorite meds

It’s helped me save fish time and time again love that you can get it in a small amount or a breeder size

Linda P. (Hayden, ID, US)

Fritz Maracyn

Kim L.
Quick shipping

Item name quickly. Needed meds ASAP for sick fish

Terrance T. (Rosemead, CA, US)
Great product

This product gets the job done. I really appreciate that the co op sells products they use. The support system is extremely valuable

FSH L. (Orange, TX, US)

As recommended by Aquarium Co-op and Aqua Huna (where I order online fish), I always quarantine and medicate new fish with Maracyn, ParaCleanse, and Ich-X. It's been very effective to prevent the spread of undesirable illness and parasites. In addition, I had some bullied fish that had clamped fins that I put in quarantine with meds and they turned around and became very robust. Highly recommend.