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API E.M. Erythromycin

$ 15.99
$ 15.99

We now prefer using Maracyn as it's the same active ingredient(erythromycin). The price of API Erythromycin keeps going up multiple times a year. Maracyn has remained a better deal.

This is what we use here at the store and at Cory's fish room to treat every fish we come into contact with. For us we've never had problems using it with inverts, scaleless fish, and plants. We've never had our beneficial bacteria die from this medication, but as with all medications take precautions in case your cycle does crash. 

Commonly used to treat:

  • Cyanobacteria
  • Fin Rot & Tail Rot
  • Columnaris 
  • Open Wounds

Dosing Instructions:

For best results remove activate carbon. For each 10 gallons of water empty on packet directly into aquarium (For 850gm jar, add one scoop [1tsp] per 20 gallons), repeat dose after 24 hours then change 25% of the aquarium water. Repeat treatment a second time for a total of 4 doses, then make a 25% water change. Treatment may be repeated if necessary. Four doses required for full course treatment. 

Treats 100 Gallons. 10 Packets, each treating 10 gallons. 850gm container treats 3270 gallons.



Customer Reviews

Based on 62 reviews
Great Product!

This is a tough medication to find. It works great and shipping was fast and affordable. Cory's med trio is my go to quarantine meds and we're having great success with it.

Works Great

I’ve used this for several years, always lowest prices and great customer service!

Excellent Service!

My order came on time and fast with updates as it shipped.

Thank you!

I feel better able to treat my fish if they should get sick, and I also now have tools to aid in prevention of most disease through quarantine. Thank you.


The guys and gals at the co-op are always on top of things, quick delivery. It came faster than my local stores could get any back in stock.

Shipping Rates
Flat rate shipping on order under $70 of $4.99
FREE Shipping over $70.

To view our shipping map and estimated delivery times click here.

Live Arrival Guarantee
We guarantee our live products will arrive alive. We ask that you do your part and minimize the amount of time our packages sit out in the elements. It can also be a good idea to avoid ordering live items during extreme temperatures. This would be when night time temps are below 35 and over 80 degrees during the day. Now these temps are not for sure death, it's just what makes it easiest for all of us during shipping.

When temperatures are cold we will use heat packs and extreme cold styrofoam liners. Shipping live goods is difficult as our warehouse could be 70 degrees and your home could be snowing, and all the stops in between. We do our best and will make it right for you and may request to try again at a different time.  During heat waves, it's best to avoid ordering live goods as ice packs etc don't do enough to mitigate it. 

30 Day Return Policy
Our goal is to provide a fair way to satisfy our customers and not lose money while doing it. We make every effort to fully disclose how our products work and what is to be expected. A damaged product during shipping is an automatic replacement from us. When it comes to a difference of opinion such as: "My fish doesn’t like this food." That we don’t refund for. However, if you decide the light you bought is a bit too green for your liking, provided it is in the original box, within 30 days and purchased from us, we will refund it at your cost of shipping.

If you would like to return a product, start the process by emailing us at shipping@aquariumcoop.com This allows us to see if there is something we can do before returning the product such as a feature you didn’t know about or send you a return label. We don’t require an RMA number, but do ask you to contact us to initiate the return. Please do not call the retail store as they operate separately from the warehouse and will not be able to issue you a return label etc.

To read our full return policy click here