Will Ozone Generators Kill Fish? Is Ozone Safe for Aquarium?

A lot has been said about ozone and how ozone generators can be applied in a space to get rid of pollutants, especially harmful bacteria and viruses. However, there has also been a lot of controversy around the safety of ozone, especially when used around humans or animals.

Ozone is a highly reactive gas that’s both naturally occurring and man-made. It can be found in the stratosphere (upper atmosphere) and the troposphere (the lower atmosphere), and can affect life forms on earth in a positive or negative way.

According to the Environmental Protection Agency, ground-level ozone is the result of photochemical reactions between VOCs and nitrogen oxides.

But whether it’s the natural stratospheric ozone or the man-made tropospheric version, ozone can cause adverse health effects when inhaled because it can react negatively with biological molecules present in your respiratory tract.

Hence, there’s always the need to apply caution when using oxygen generators both for our health and for the safety of our pets.

That said, do ozone generators kill fish? Is it safe to use an ozone generator in a room that has a fish tank or aquarium? Should ozone be applied directly in a fish tank to kill harmful bacteria?

Indeed, many of these questions have been left unanswered for so long, and we’ll try and put a stop to the confusion.

Can Ozone Harm Fish? Will Ozone Machine Kill Fish?

Ozone can be pretty harmful to fish when released in high concentrations. A high concentration of ozone within the same space as a fish tank can transform the water into hydrogen peroxide which can kill the fish.

Disposing of a high concentration of ozone in a small pond or stream can also be detrimental to the health of the fish in the water. The way to treat ozone is to always apply the principle of the 3 Ps; People, Plants, and Pets.

You should follow the 3 Ps. Ozone should not be used or applied in large quantities in the same space as fish.

In small quantities, ozone may not have that much effect, especially if not applied in the same room or space as the fish. One very tricky fact is that ozone can help with water sterilization, ensuring that water becomes crystal clear.

This is why some people are tempted to use ozone directly in fish habitats. We do not advise you to. Overdosing ozone can be very harmful and kill the fish.

Can You Use an Ozone Generator with A Fish Tank?

We strongly advise against using an ozone generator with a fish tank. Some people get away with very small quantities of ozone in their fish tanks, especially the very large tanks.

They are able to clean up the water and reduce bacteria levels significantly. Using ozone, if the amount is accurately achieved, means avoiding the use of other harmful chemicals which can have adverse effects on the fish.

However, it may be impossible to get the right dosage and this can cause serious consequences. If you must, you can use an Oxidation Reduction Potential (ORP) monitor to measure safety.

The ORP level of natural seawater is around 350-40 mV. However, your fish tank may be showing an ORP level of around 200 mV, which indicates low oxygen.

Ozone can help to raise the ORP level to a safe range of 250-350 mV as long as you’re able to adjust it properly. The ORP monitor will automatically shut off the ozone generator once it reaches the desired level.

Exceeding an ORP level of 400 mV means trouble for your fish and you should never do that. Be sure to stay within the recommended range to keep your fish alive and well.

Another way to ensure only the right amount of ozone is used with a fish tank k is to apply the simple formula of 5 mg/hour for every 1 liter of water. This is a simpler way to get things right if an ORP monitor is absent.

Let us emphasize that we do not recommend the use of ozone in or near a fish tank, but only if absolutely and only in very small doses.

Does Ozone Kill Fish in An Aquarium?

Yes, ozone can kill fish in an aquarium if it is applied, in large amounts, directly or within the same space where there’s an open aquarium. Avoid applying ozone directly in an aquarium or too close to it unless you’re sure of the right dosage.

Ozone can cause rapid decomposition in water as a result of its low dissolution property. Such reactions can cause severe and even fatal damage to the fish. There are several other non-chemical and more effective water treatment technologies you can adopt instead of ozone.

The simple truth is, ozone reacts to external materials when in high concentration as a result of certain chemical properties; it is the same properties that make it harmful to living organisms as well, such that it can damage the human lungs if inhaled.

It is also the same chemical properties that make ozone harmful to fish. It is best to keep it away from your aquarium. And if you must sterilize the aquarium, use a safer, non-chemical agent or method.

Does Ozone Kill Beneficial Bacteria in Aquariums?

The answer is Yes and No. Ozone can kill beneficial bacteria if highly concentrated. The effectiveness of ozone relies heavily on quantity. A little dose and you may just have the perfect aquarium, but a little more can damage the entire thing.

A maturing aquarium tends to have more accumulation of dissolved organic colloidal solids, which causes a decrease in the performance of nitrifying bacteria which converts nitrite to nitrate.

This further causes the buildup of toxic nitrite and increases biological oxygen demand which leads to decreasing oxygen levels.

Such situations can cause water condition shifts, in terms of salinity, alkalinity, and PH, which could lead to mortality in some cases. Ozone is sometimes applied to break down these organic wastes, and remove colloidal and fine solids, nitrite and dissolved organic compounds.

It can also serve as a disinfectant. However, adding too much ozone to your aquarium will not only kill harmful bacteria but may also have a negative effect on beneficial bacteria. These are organisms that your fish needs to live a healthy life.

Final Words:

Ozone has been touted as a formidable purifier and disinfectant for many years, but knowing its adverse effects on your pets such as fish can help you make the right decision. We advise you not to use ozone around people, pets, and plants, and that includes fish.

But, if you must, ensure you apply only the right dose that is too insignificant to cause any damage but just enough to get the job done. This can be a tricky route, so it’s best to avoid it altogether so you don’t cause harm to your fish.