FRITZ AQUATICS Mardel Maracyn Two Antibacterial Aquarium Medication, 24 count

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Treats body fungus “columnaris”, fin and tail rot, popeye, dropsy, septicemia and gill disease in freshwater and saltwater fish.

Formulated with maracyn-two, a broad-spectrum antibiotic that is absorbed by the fish through the skin to enhance effectiveness.

Easy-to-use powder formula dissolves fast to start treating symptoms like clamped fins, swollen eyes, corner hiding and others.

Safe to use around invertebrates including shrimp, and is ideal for tetras, cichlids, catfish, goldfish, angelfish, clownfish, damsels and more.

Available in 8-pack and 24-pack boxes to accommodate any size tanks.

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Keep your tank healthy and thriving with the Fritz Aquatics Mardel Maracyn Two Antibacterial Aquarium Medication. The fast-dissolving powder formula uses maracyn-two, an advanced broad-spectrum antibiotic to treat common bacterial infections including body fungus, gill disease, popeye, tail and fin rot, and dropsy. It works in both freshwater and saltwater fish, and helps treat common symptoms like clamped fins, swollen eyes and patchiness. Plus, it won’t harm invertebrates so you can use it around shrimp and other antenna-wearing aquarium buddies.


Item Number


Aquarium Type

Freshwater, Saltwater

Made In

United States

Fish Type

Tropical Freshwater, Marine Fish, Goldfish, Betta

Product Form



Consult a veterinarian or fish expert for assistance in diagnosis of disease causing organisms and treatment options.


First day add the contents of two packets per 10 gallons of water.
Second through fifth day add one packet per 10 gallons of water.
Repeat this five day treatment once if needed.

Cloudiness may occur while using Maracyn® Two.

Important: Treat for five days even if visible signs disappear. May be used concurrently with Coppersafe®, Maracyn® or Maracyn® Oxy. Maracyn® Two will not harm invertebrates.

Maracyn® Two may cause excessive foam production in protein skimmers, stop use of skimmer during treatment if excessive foaming is a concern.

Questions & Answers

4 Customer Questions

Does this contain erithromycin? What are the active ingredients?

Answer by • Feb 11, 2022

This medication does not contain erythromycin. The active ingredient is Minocycline.

Is it safe to use with snails and shrimp?

Answer by • Jun 16, 2022

This medication is safe to use with invertebrates when used as directed.

Can you use for a Betta in a tank with no filter/circulation?

Answer by • Mar 30, 2022

This medication is safe to use with bettas. Maracyn may cause excessive cloudiness and foam production so it is recommended to remove carbon during treatment, but maintain adequate water flow or aeration.

can you use this in planted aquariums?

Answer by • Mar 09, 2023

Some more sensitive plant species may display yellowing, but this condition generally improves after the treatment; remove any plants if concerned.

My fan-tail goldfish suffered from fin rot for 8 long months. I tried 3 other highly-recommended medications and kept the water pristine, all to no avail. Her fins continued to deteriorate. I finally tried one course of Maracyn Two and within a week her fins showed new growth! They are completely grown in now and she looks beautiful and healthy again.

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