The effects of plasticizers on aquarium life

By: Ashley Gustafson

For many, home aquariums offer a sense of serenity to any room. Something about the movement of the water, the flow of fish swimming, and the gentle humming of the water filter radiate a sense of peace. Not to mention that the aquarium hobby itself is rewarding and fun. It may require a good deal of research, time, and substantial amount of money to start up a home aquarium but that hasn’t set the hobby back in popularity. While there are numerous aspects to consider when it comes to tank equipment today I will touch upon the use of PVC in both freshwater and saltwater home aquariums alike.

knop_tubing_1It is not a surprise that some materials used in the aquarium hobby may be more suitable for freshwater aquariums than salt water aquariums. One example you might not have thought about is flexible PVC piping. For those of you who are not familiar PVC or polyvinyl chloride, it a staple material in not only aquarium construction but building construction. It has nearly endless applications from window frames to flooring to water distribution. This of course is because it is durable and long lasting to boot. It’s very strong, stable structure is rarely affected by outside elements and has even has been shown to be resilient to salt water which is notorious for being corrosive in nature. PVC plates are good for reef keeping as it remains solid in salt water for several years. In fact this is a problem for our world’s oceans. When PVC waste finds its way into the ocean it will not decompose or break down thus polluting and altering the natural environment.

Now PVC may sound perfect but just like any material it has one major drawback. PVC is very strong and rigid and because of this it is brittle and lacks flexibility. This is great for window frames and flooring but for aquaria piping it is not ideal. To fix this problem, engineers were able to add a group of chemicals known as plasticizers to PVC structure, increasing its flexibility. PVC is made from a long chain of molecules. Plasticizers are intertwined with the molecular structure of PVC but not covalently bonded. This means that plasticizers do not share atoms with the PVC making them weakly attached. When plasticizers are added the PVC material expands because the distance between the individual molecular chains increases and they become equally transferable (figure 1). This is what makes the new PVC with plasticizers soft and flexible. PVC piping is customizable for specific purposes or needs. This is done by adding stabilizers and impact-modifiers which include plasticizers like phthalates. PVC with plasticizers is ideal for aquariums as it allows bending and flexibility needed when arranging and setting up aquaria. Flexible PVC piping has been a stable in aquaria for decades. Flexible PVC piping is much more prevalent in freshwater aquariums than saltwater aquariums since they can be very difficult to use productively in saltwater aquariums. When aquarists fixed one problem with the creation of flexible PVC, they uncovered a whole new problem.


Figure 1. Molecular structure of PVC.

As I mentioned above, plasticizers are unstable when intertwined with the molecular structure of PVC. That is, they are highly susceptible ok leaking out of the PVC framework and into their surroundings whether it is liquid or air. For example, when plasticizers leak into the air they are absorbed by other materials around them causing an odor much like that of the “new car smell”. The singular, molecular structure of PVC is resilient to salt water itself but it is rigid since it contains very few plasticizers. On the other hand flexible PVC using phthalate plasticizers can leak out when exposed to salt water. When this happens not only is your aquarium exposed to phthalates but the once flexible PVC piping will become brittle and rigid. It is important to note that phthalates are chemicals suspected of having dangerous repercussions on living organisms. They are likely to have a hormone like effect on living organisms. In humans they could cause obesity, infertility, and even onset diabetes. Phthalates also cause kidney and liver damage, and are suspected to cause cancer as well. All this can occur when exposed to Phthalates because they can pass through skin, bodily fluids, and the respiratory system. In fact, the European Union (EU) found in a study that certain phthalates trigger feminization in children before and after birth. For this reason, PVC containing phthalates was banned for use in children’s toys throughout the EU in 1999. While as humans it is no wonder we are concerned with our own well-being, it would be very interesting to study how phthalates leaking from flexible PVC could affect the health and reproduction of marine life since little conclusive research has been conducted thus far.

Now released plasticizers in a saltwater tank become a bigger problem the smaller the tank. The general rule of thumb is the smaller the tank the greater the concentration of released plasticizers when using flexible PVC. In larger tanks this becomes less problematic but in small tanks, like nano-reef tanks, the impact could be fatal. As mentioned before very little conclusive research of the effects of released plasticizers from flexible PVC has been done so the specific consequences are quite uncertain. So far possible consequences include stagnant growth of corals, inexplicable mortality in mollusks, and obscure slime algae infestations. However one way that has proven to control moderate amounts of plasticizers in reef aquariums is a permanent carbon filtering system. However, this is problematic in many tank set ups as is can diminish trace elements which are essential to healthy aquariums. The best route to take is using a different, harmless piping material in saltwater aquariums. That route is using silicone piping instead of flexible PVC piping (figure 2).

While flexible PVC piping with plasticizers is ideal for freshwater aquariums it causes more harm than good in saltwater aquariums. It is still important in saltwater aquariums to have flexible piping that won’t break when bent. Silicone piping offers just that! Silicone will not change when exposed to salt water even after long periods of time. While it is much more expensive than flexible PVC tubing it is worth the investment. When choosing silicone in a saltwater aquarium you are getting much more than just a piece of hose, you are investing in your marine tank and thus marine animal’s health, growth, and longevity. Building both freshwater and marine aquariums is an exciting, rewarding, and fun hobby. It is important to do your research before deciding on your new tank’s equipment and aquatic life in order to provide a safe and healthy aquarium that you can enjoy for many, many years to come.


Figure 2. Silicone tubing (left) flexible PVC tubing (right).