Curing Velvet disease using hydrogen peroxide
Velvet disease also known as Piscinoodinium pillulare is a common, deadly and contagious disease in freshwater aquarium hobby. Infected fish exhibits symptoms such as a gold or gray dust-like coating on their skin, labored breathing, lethargy, and loss of appetite. Death can come slowly and fish can perish in a week or two without treatment. The parasite itself is a dinoflagellate which protozoa (not to be confused with protozoans), are actually more like single-cell algae. Furthermore, they have a cellular wall called a theca and a chloroplast, allowing them to survive without a host via photosynthesis.
The issue with chemical treatment using COPPER
Treatment for Piscinoodinium pillulare usually involves some form of chemical in addition to increasing the temperature or the addition of complete blackout over a period of at least 30 days. This is because Piscinoodinium pillulare has a life cycle in which only the free-swimming “dinospore” can actually be killed with the chemicals. The most common and widely used chemical that many aquarists have used including me is chelated Copper Sulphate and it is what I typically have been using for many years, however with mixed success. Let's discuss why Copper sulphate can be ineffective for velvet treatment.
#1 Dosing needs to be very accurate
Copper sulphate can only effectively kill dinospores if it is at the minimum concentration of 2.00 - 2.50 ppm. IMO with the wide use of copper in the treatment of fish, velvet disease has become extremely resistant to lower levels of copper so the correct concentration must be used. However, high levels of copper can become toxic and usually have long negative effects on the fish including loss of appetite.
Other popular copper treatment
Cuprion (0.20 ppm)
Cupramine (0.5 ppm)
#2 The treatment duration is very long
Treatment duration for Piscinoodinium pillulare must be a minimum of 30 days or longer, this is because the dormant stage of dividing tomont can be up to 14 days depending on temperature.
#3 The parasites are only killed by copper by being exposed to it over a period of time and ONLY in the dinospore stage.
Copper does NOT kill the free-swimming parasite on contact. This is actually a HUGE issue in heavily overstocked or undersized tanks as free swimming dinospores can quickly re-infect fish before they are even killed by the copper. This is not often talked about when it comes to the treatment of velvet disease
#4 copper stays in your water permanently
The only way to remove copper is through water changes, I am not even sure if activated carbon can fully remove copper. Not only that, copper often builds up in the substrate and gets trapped there. Long-term exposure to copper in fish is something that is not good as metal concentration can build up inside fish.
Hydrogen peroxide, possibly the next big thing in fish disease treatment.
My discovery of hydrogen peroxide actually came from the salt water marine aquarist folks. They have been dealing with their own version of velvet disease called Amyloodinium ocellatum. This dinoflagellate parasite is a close relative of the freshwater Piscinoodinium pillulare and has similar life stages. I would like to give credit to the person by the name of “humblefish” who gave out suggested dosage for dips to remove the feeding trophonts. The use of hydrogen peroxide for the treatment of various diseases is actually quite new to freshwater and saltwater aquarists as well as in agricultural aquaculture with many research papers discussing its use written in the past few years. I will post the link to one of the research papers at the end of this article.
Here is the link to Humblefish saltwater treatment of velvet for those that are interested.
How does hydrogen peroxide work?
Hydrogen peroxide is a strong oxidizer, it's actually stronger than bleach when it comes to its oxidizing capabilities. Oxidyzing agent (not to be confused by oxidation) works by stealing electrons from another substance, in this case it is organic compounds. The reaction is instantaneous and produces h2o (water) and o2 (oxygen) as a by-product. The oxidizing effects of hydrogen peroxide breaks down cell walls, making them very effective in killing simple organisms such as microbes.
This is why hydrogen peroxide has been used in the past in the planted tank folks to get rid of algae. Algae are usually simple organisms that are usually only one to a few cells thick, making them much more vulnerable than complex plants and animals which have natural defense barriers.
So what does that mean for its effect on velvet?
Hydrogen peroxide can break through the barrier that the feeding trophonts and the resting tomont create and essentially destroy it. This is VASTLY different than any other methods used such as copper as it no longer requires prolonged exposure of up to a month to eradicate the disease. You can eradicate it within a day to a week depending on factors such as tank size, substrate, organic matter, volume pH, and such. In bare bottom tank, velvet can be eradicated in just a day under ideal circumstances
What are some other benefits of hydrogen peroxide as a treatment?
The biggest benefit besides quick eradication in the trophont and tomont stages is that it breaks down to water and oxygen, both of which is non-toxic to fish. In fact, it can increase the oxygen percentage in the tank temporarily to 300%. This can actually aid fish that are heavily infected and has difficulty with breathing.
What is the half-life and stability of hydrogen peroxide?
Before we go into dosing, we need to understand the chemical stability of hydrogen peroxide. Hydrogen peroxide degrades under the presence of heat, light, friction, and pH. It is slightly acidic, and its stability improves with increasing acidity. Its degradation in water depends greatly on surface area and the amount of organic material that is available for it to react with. That means a dosage for one tank with specific organic content, surface area, ph, flow rate, and light availability will be vastly different than another tank even if the amount of water is taken into account. This is important to know because it will bring me to my next point.
What is the dosage that we should use?
Based on my experimentation, for freshwater application dosage should not really exceed 100ppm for dips and 15-50ppm for prolonged exposure. This is reflected upon by experiments done by Roy P. E. Yanong at the University of florida. When observing anecdotal reports by saltwater keepers, a dosage of up to 150ppm are for dips (as recommended by humble fish). This is because salt water has a much higher pH and TDS, and the oxidizing effects are not as strong as they would be in freshwater.
What is generally better is a dip or prolonged exposure.
I wholeheartedly believe that prolonged exposure is better for complete eradication, dips can be very effective but the high concentration of hydrogen peroxide in dips has caused me to accidentally kill some fish. I discovered that different fish have different tolerance to hydrogen peroxide. Some of the larger scaly fish such as Betta unimaculata and antutas can withstand dips up to 150ppm while smaller fish and mouth brooders can die in one hour at 50ppm. This is simply too dangerous for me to work with. However, I found that reducing the dosage down to 15-50 ppm and leaving the fish in that concentration over a 24 period can be just as effective and it's a safer bet over the long term although the effects are not as quick. Some fish like betta splendens and betta coccinas can tolerate a single 50ppm dose for 24 hours (keep in mind it will NOT remain 50ppm for 24 hours due to the break down to h2o2), but I would only do so with the addition of heat as it helps speed up the breakdown of hydrogen peroxide. Below is a quick overview of the dosage I would recommend for dips.
Large mouth brooders (unimacs, antutas)
150ppm for 45 minutes
Mouthbrooders (foerschi, rubras etc..)
75 ppm for 45minutes
Small mouth brooders
50 ppm for 45minutes
75 ppm for 45 minutes
50 ppm for 45 minutes
Small nano fish (do not recommend dips)
For prolonged exposure, I use a concentration of around 15ppm to 50ppm depending on the fish. Mostly, large mouth brooders, coccinas and splendens will typically be exposed to this amount. Small mouth brooders like Channoides and Albimarginata will be exposed to 20ppm and small nano fish 15ppm or even less.
How do I calculate dosage
Use this as a rule of thumb, 6.5ml of 3% hydrogen peroxide gives roughly 50ppm to treat 1 gallon of water (BARE BOTTOM nothing else in there). I would only use a ⅓ of that for smaller nano fishes and even less for some fish.
What is the typical tank setup for treatment? How do you use hydrogen peroxide for treatment?
When I treat my fish for velvet I typically isolate the fish (or fishes) to 1 gallon bare bottom tank, with nothing but water and the fish. In these bare bottom tank, there should be nothing in there that would cause the hydrogen peroxide to react, that includes any substrate or organic materials. That's because it wants it to react ONLY with the velvet (of course it will react with the fish too). That also means NO sponge filters as surface agitation will cause the hydrogen peroxide to break down too quickly but also will kill all the beneficial bacteria anyway. I also put the tank above a heating pad set to 84 degrees and RO water acidified to a ph of 5.5 (using hydrochloric acid)
Below are the setups, steps, and results!
Tank set up is 2.5 gallons bare bottom filled up with a bit more than 1 gallon of water keeping the ph at 5.5 and the temp at 84. Low ph is used to increase the stability of hydrogen peroxide.
The heating pad is shown below as a black mat. Heating pad makes sure that most of the peroxide is broken down after 24 hours to speed up the reaction. However, I do not think it is necessary to always use heat.
After you have set up your tank, inject the 6.5ml of hydrogen peroxide 3% into each tank and add the fish. After 48 hours the velvet should clear up, if the velvet still persists re-dose with HALF dosage (3.25ml) then check again after 48 hours
3% hydrogen peroxide, no other additive
Using a 10ml syringe i pull out 6.5 ml of hydrogen peroxide
You can see how powerful an oxidizer hydrogen peroxide is, it literally bleaches my skin!
Betta Foerschi male before treatment, you can see he is covered with velvet
The same fish after 48 hours
Male Betta mandor before treatment
48 hours AFTER treatment, still has some infection so a follow up dose was required
Here is a Betta Uberis before treatment
Here he is 48 hours after treatment
As you can see, hydrogen peroxide is THE best treatment for velvet disease because not only does it destroy the trophonts and the tomonts it does it FAST. This means your fish will not suffer for 3 or more weeks with the infection increasing its chances of survival.
Hydrogen peroxide is highly promising and can potentially be used as a method of quarantine, this is because not only does it treat velvet but it's highly effective vs other infectious diseases such as bacteria and protozoans. However, because it's a relatively new and experimental nature we do not know the correct dosage for quarantine or to treat a specific disease.
One of the biggest downsides to hydrogen peroxide treatment is that it will kill your biological bacteria at an effective dose. This means we have to figure out new methods and ideas to treat disease in established tanks as well as use it as a way to quarantine fish. This is something that I would definitely explore in the future.