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 100-gram bulk container treats 1,000 gallons. 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 442 reviews
Kristy D. (Savannah, GA, US)
Keep this on hand

This medicine has saved more than one of my fish. I try to keep it on hand. It was literally lifesaving when I had a filtration problem and almost lost my whole aquarium.

Jacqueline V. (Pittsburgh, PA, US)
Fast shipping!

I placed my order on Saturday and received it Monday! I’m so thankful for this cuz my betta got fin rot and I was scared it was gonna be too late, but this came in time and he seems to be getting better! I love that this medicine is also not harmful to invertebrates/ plants so I didn’t have to put him in a quarantine tank, just had to take out the filter media. Also packaging was neat and secure and I got a free Murphy vinyl sticker yay! I’ve been buying plants, stickers, and meds from aquarium co op for a little over a year and am always happy with my purchases :)

Brian G.
Great product

5 star well pleased

Amber D. (Sacramento, CA, US)
Fritz Maracyn

My Beta has been laying on the bottom of tank, having a hard time swimming. I got this and a few different meds for him. I used it for a little over a week and I definitely feel like if his issue was due to parasites or bacterial infection it would have definitely worked. He is still not doing well but he is three years old if not older so it may be his age, I don't know. The cost comparison to other companies is much more reasonable and I'll definitely order from Aquarium Co-op again.

Julie (Van Nuys, CA, US)
great med

I use it sparingly because of the risk of antibiotic resistance, but this is a great med that has helped me thru many issues, quarantine periods, and "just in case" situations. Just recently, I had a batch of Corydoras habrosus that were dying one by one, about one every three days. No external signs of issues, and no sunken bellies or other parasite indications, so I suspected an internal bacterial infection. I gave the tank a round of Maracyn according to the instructions on the box and I'm so happy to say I haven't lost another cory since. It dissolves very quickly into the water, can be mixed into food for oral administration, and does not harm shrimp, snails, or plants.

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