Oxygen Tablets for Fish Ponds, Lakes & Aquaculture – Are They Safe?
As discussed in many of our various other articles, the importance of oxygenating pond water cannot at all be overstated or stressed enough. Without adequate oxygen, your fish, plants, and any other pond residents that you have will greatly struggle to survive, while potentially undesirable organisms such as cyanobacteria and mosquitos are more likely to thrive.
Once dissolved oxygen levels fall below approximately 6 ppm (parts per million), the water becomes largely unhealthy and unfit for habitation by most creatures and it begins the process of “dying,” otherwise known as eutrophication. To prevent this, there are a variety of actions that you can take.
Oxygen tablets are a fairly uncommon method of adding oxygen to water, and as such many people are unfamiliar with them. Overall water quality and dissolved oxygen levels are of course tied to many other things in your pond, such as nutrient levels, temperature, pH levels, water hardness, fish stocking load, climate, and so on. With all of this in mind, you should be careful and cautious when considering adding anything new to your pond, as it’s a delicate ecosystem with easily influenced chemistry. Here we will discuss how oxygen tablets work, if they’re safe, and potential alternatives.
How Do Oxygen Tablets Work In Ponds?
The primary chemical compound in oxygen tablets is hydrogen peroxide, with various sodium compounds being secondary. Other tablets may contain calcium peroxide or magnesium peroxide, both of which are less water soluble and are therefore able to release oxygen more slowly but for longer periods of time.
Essentially, the hydrogen peroxide (or a similar substitute) and sodium compounds react with the water and produce many thousands of bubbles as the tablets dissolve. Imagine dropping a seltzer tablet in a glass of water and the immense amount of bubbles that it releases – while the chemical compounds are different from the oxygen tablets, the reaction is similar. The reason hydrogen peroxide is typically used in these tablets over other compounds is that it is very reactive to water; its chemical formula is H2O2 (the same as water but with an extra oxygen atom), and its solubility means that it readily parts with these oxygen atoms when placed in water.
To further drive home just how many bubbles these tablets produce, they’re frequently used to unblock clogged drains and treat septic tanks as the bubbles will help to work through and force out obstructions. Most of the products available mention that they only work for a few hours, though some claim to work for closer to 12 hours depending on the exact compounds that are used to make the tablets.
Are Oxygen Tablets Safe for Ponds & Fish?
First and foremost, oxygen tablets should never be the sole source of oxygen in your pond – they will not be enough. Their primary purpose is to help provide oxygen to fish temporarily as they’re being transported, or as an additional short-term oxygen boost in aquariums and small ponds. These don’t by any means replace or fully replicate actual, adequate pond aeration via pumps and water features.
In terms of pros, these tablets are great for immediate, rapid oxygen release. This means that if you’re transporting fish, your oxygen levels have suddenly dropped, or there’s been a power outage and your air pump won’t work, these tablets might work for you in a pinch. They also have a virtually indefinite shelf life, so long as they’re kept dry and at standard room temperature, so you could easily keep them on hand for emergencies. The FDA has approved certain dosages to treat aquatic parasites, molds, and algal overgrowth, but great caution should be used and a professional should first be consulted.
What Are The Dangers of Oxygen Tablets?
It is important to note that there are predictably more cons associated with this oxygenation method than there are pros. For starters, hydrogen peroxide is a bleaching agent, and could cause skin issues and gill damage for fish as well as potentially bleaching any fish eggs that are present. While some brands claim that oxygen tablets help to promote a healthy slime layer in fish, there is little current evidence to support this.
Only a handful of known scientific studies have been conducted on the impacts of hydrogen peroxide to fish and overall water quality, and so the exact concentration at which hydrogen peroxide becomes toxic to fish is largely unknown – as with most things, the few studies that have been done have concluded that it varies greatly depending on the fish species and overall water parameters.
Do Oxygen Tablets Work in Large Ponds & Lakes?
Overall, in order to make a significant difference in dissolved oxygen levels in something relatively large (in comparison to an aquarium) like a pond, it appears that quite a high dosage of these tablets would need to be used. This is of course not advised, as the potential danger to fish and other organisms like frogs, macroinvertebrates, plants, birds, and anything else that visits the pond is simply too high as far as we can tell.
In addition, by the same means with which hydrogen peroxide is able to kill off harmful parasites and organisms, it can also kill off beneficial ones, such as the vital bacteria in your pond. Extreme caution should be used, as your water chemistry could become quite altered, thus damaging your pond’s simultaneously delicate and complex ecosystem.
To sum it up, oxygen tablets are safe…when used in the right quantities under the exact right conditions with the right species and within the correct time frame. That is to say, in most cases they shouldn’t be used as there will almost certainly be some form of negative impact, whether minor or major. Unless you’re in some sort of extreme circumstance in which there’s no other way you can get adequate oxygen to your fish, it’s best to avoid using these tablets.
What Are Alternatives to Oxygen Tablets?
There are a plethora of much safer and vastly more effective oxygenation methods for fish ponds, such as those listed in some of our previous articles. Plants, both submerged and emergent, are wonderful for naturally increasing oxygen levels while also filtering out excess nutrients and pollutants as well as creating habitat, shelter, and food for many organisms (including your fish!).
Air compressors and pumps will add oxygen and many will also help to circulate the water as well. Fountains and waterfalls incorporate both water movement and oxygen as the water tumbles into the pond, trapping oxygen molecules inside of the water droplets that then enter your pond and rise back to the surface. Healthy algae species (and in healthy amounts) can also add oxygen to your pond.
Ensuring your pond water isn’t too warm will help to encourage adequate oxygen levels; once water temperatures exceed approximately 85° F (29° C), dissolved oxygen falls below 6 ppm – the point at which most fish begin to suffer from hypoxia. Incorporating several of these methods will give you the best results.