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How Usnic acid and Mucilage which are both found in Usnea lichen can be used as effective alternative aquarium and pond fish treatments.

By Carl Strohmeyer-PAMR 40+ years experience
Updated 2/29/20

Usnea Sprig on branch, for aquarium fish and human gram positive bacteria

Scientific name: Usnea barbata.
Usnea is a lichen of the family Parmeliaceae that grows in damp temperate woodlands and contains usnic acid (C18H16O7). I have found it effective for bacterial (some gram negative and most gram positive), fungal and even parasites such as ich.
The other active ingredient (besides usnic acid) is mucilage.

Usnea in forest
As a natural antibiotic it has also proven effective against gram positive bacteria, such as Mycobacterium tuberculosis (making Usnea a great alternative to Isoniazid).
Scientists believe that usnic acid works by disrupting cellular metabolism, either by preventing the formation of ATP which is the cells' energy source or by the stopping the action of oxidative phosphorylization. Usnea may also be a better choice than the drug metronidazole (as per human studies) for parasites and anaerobic bacterial treatments in aquariums.

Usnea contains potent antibiotic properties on gram positive bacteria.
As well, the Usnic acid found therein has shown antiviral, anti-protozoal, anti-inflammatory and analgesic (pain killer) activity.

It is also noteworthy that Usnea is edible, with no known toxic side effects from ingestion in animal and human studies and as well is an excellent source of Vitamin C.
In fact some monkeys consume similar lichens as their primary diet. Reference: Golden snub-nosed monkey

More information about Usnea;

Test tube studies have suggested an anti-cancer and an anti-viral activity for usnic acid. This may also make Usnea useful for the hard to treat aquatic viral disease; Lymphocystis (which is usually not fatal in otherwise healthy fish). The human studies can also be transferred to fish for tumors. I personally have not tested this enough as of writing this article, but based on human studies and the few tests I have done, Usnic acid shows promise here.


Here are preliminary results based on my tests and tests on humans or veterinary application that can be extrapolated to fish:


Brewed Usnea tea for treatment
I boil one small sprig (about an adult thumb size) in 6 oz. of water and add this to every 10-20 gallons of water every day until cure is effective +2 days. Make sure to remove the Usnea sprig from the “brewed Usnea tea”, otherwise this will allow the tea/medication to spoil. I also recommend refrigeration after brewing of any unused Usnea brew.

1 tablespoon per 6 oz. of this preparation can also be used for a 1 quart bath as an alternative (This is my preferred Use of Usnea!).

Please see these articles for more about the use of baths for treating fish:
*Fish Baths, Dips, Swabs; For Disease, Ammonia, etc. Treatment
* Aquarium Disease Prevention; Quarantine

I have also simply added sprigs of Usnea to filters or just floated in the aquarium as one would use peat to acidify the water. I measure pH during this time so as to not use to much as to rapidly drop pH.

Please keep in mind that at this point I would consider this an experimental treatment, mostly in actual dose, so ANY positive or negative feedback is welcome, especially as per dosing effectiveness.
As to the actual effectiveness, there is enough evidence in my own trials and even more so in well researched human trials that this can and will be an effective treatment, the most effective dosing amounts is what is still the biggest question at this point.

I will also point out that my results have generally resulted in 25% success, HOWEVER this is from using Usnea as a last resort medication when others have failed, so this is actually relatively good number when that is considered. I will soon start using this more as a "first treatment" especially for gill injuries/infections/inflammation to find more results as to use of Usnea in mode of treatment.
Feedback from a few clients has been better when used as a bath, with often positive results when used for generally gram positive infections or even Fish Tuberculosis (I am not recommending this for human TB, please see a doctor for this).

The only dangers that have been established (in human studies) are in rare cases liver damage, which would make this a poor choice for dropsy.

If interested in some Usnea for your own trials, you can purchase Usnea near the end of this Organic Medications Article:
Aquarium Medications 4; Purchase Usnea

As for related Disease Prevention Suggestions; the use of UV Sterilization is a proven method of fish disease prevention not only due to removal of many water born disease pathogens, but by improving the Redox Balance and thus the Fish' natural immunity.
The key is a properly installed, quality UV Sterilizer, not one of the many Cheapie models such as the AquaTop PFUV-40 Hang On Filter.
With a quality UV such as the TMC Vecton or Advantage UV, it is also imperative to change your UV Bulb every six months for maximum effectiveness.

See these references and product links:

*Aquarium & Pond UV Sterilization
*Quality UV Sterilizers
*TMC Vecton or Advantage UV Sterilizer
*UV Bulb; Replacements

More About Usnea:
What is Usnea?

Other Recommended Reference Sites

*Aquarium Medications Page 1

*Aquarium Lighting Information from A to Z

*Aquarium Filtration; Filter Use Information

*Aquarium Fish Nutrition

FISH AS PETS; News of Interest to the Aquarium Hobby


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In Chronological order of writing with the newest at the top

  1. How to Treat Sick Fish
  2. Whirling Disease in Fish
  3. Reef Aquarium Chemistry Maintenance
  4. Use of RO, DI, Softwater in Aquariums
  5. Lighting Theory of a Planted Aquarium- RQE, PFY, PAS, & PUR
  6. Aquarium or Pond Bio Load
  7. Tuberculosis in Fish
  8. PUR vs PAR in Aquarium Lighting
  9. Head Pressure in Aquarium and Pond Water Pumps
  10. Fin/Tail Rot For Betta & ALL Fish
  11. Angelfish Virus/Aids
  12. Activated Carbon
  13. Fish Baths/Dips as an aid to treatment
  14. Streptococcus gram positive bacterium in aquariums, Eye Infections
  15. Hydrogen Sulfide
    production in anaerobic De-Nitrification for Aquarium/Ponds
  16. Fish Shipping
  17. Aquarium Size, Fish Stunting
  18. Aquarium Algae,
    BBA & Brown Algae in particular
  19. Aquarium Salt (Sodium chloride) in Freshwater Aquariums
  20. Betta Habitat; Wild Bettas to Domestic Betta environment parameters
  21. HITH; Hole in the Head Disease
  22. Aquarium Protein Skimmers, Ozonizers
  23. Power Head/ Water Pump Review
  24. Molly Disease/ Mollies in an Aquarium
  25. Basic Fish Anatomy, Fin Identification
  26. Aquarium Moving/ Power Failures
  27. Octopus as Aquarium Pets
  28. Aquarium Nitrates
  29. Ichthyophonus protists, fungus in fish
  30. Aquarium and Pond Filter Media
    Types; Mechanical, Bio, Chemical
  31. Aquarium Water Conditioners (also Pond)
  32. Fish Parasites; Trematodes & Monogeneans; Annelids and Nematodes;
    Flukes, internal worms, Detritus Worms (often confused with Planaria), Micro Worms
  33. Aquarium Silicone Application;
    DIY Aquarium Repair & Glass thickness
  34. Pond Veggie Filters; DIY Bog Filter
  35. The difference between Plaster of Paris and Aquarium Products such a Wonder Shells:
    Identification, prevention & Treatment
  37. AQUARIUM TEST KITS; Use & Importance
  38. SEXING FISH; Basics
  39. Chocolate Chip, Knobby and Fromia Starfish
  40. Freshwater Velvet & Costia
  41. Usnic Acid as a Fish Remedy
  42. Aquarium Heaters; Types, information
  43. The Lateral Line in Fish, Lateral Line Disease
    or Head and Lateral Line Erosion (HLLE)
  44. Tap Water use in Aquarium; Chloramines, Chlorine
  45. Can Black Ghost Knife fish give an electric shock?
  46. Bio Wheel Review; Do Bio-Wheels really work?
  47. How do Fish Drink?
    Use of RO Water
  48. Cyclops, and Predatory Damselfly larvae
  49. Betta with Dropsy;
    Treatment and Prevention of DROPSY in all fish
  50. pH and KH problems in African Cichlid Aquarium
  51. Aquarium Gravel, which size?
  52. Blue green algae, Cyanobacteria in Ponds/Aquariums

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