Polylactic Acid (PLA) is a popular 3D printing material because it is generated from renewable sources. As a thermoplastic, it changes from a solid to a liquid at high temperatures and back to a solid as it cools.
Despite the fact that it comes from renewable sources, it’s not considered to be the safest option in a reef tank or any aquarium for that matter. Now, you’re probably scratching your head, wondering why there are so many blogs out there claiming the opposite. Well, there’s truth to be found there as well.
What it really boils down to is that PLA is more trouble than it is worth because there are several things that can go wrong with it that aren’t present in other materials. PLA degrades in water—which makes sense, considering that it comes from corn starch and sugar cane.
If the PLA has nylon in it, it will swell, simply because that’s what nylon does when it is submerged in water. If there are dyes in the PLA material (if you want any colors then there are going to be dyes) they will diffuse as the PLA breaks down. Then, there’s the potential for harmful additives, as well.
Is PLA Okay in Saltwater?
PLA is less safe in saltwater, as it will eat into the material of the PLA faster than freshwater. If you place a 3D printed object, constructed with PLA, into saltwater and another in freshwater, you will be able to see the difference in the speed at which they break down.
Of course, the breakdown will take months, some of which you won’t be able to see as it slowly leeches out into the water. There are ways around this, such as using fixative sprays or certain varieties of wax. As aforementioned, PLA is okay, so long as you are in a constant state of preventative maintenance.
If you stop and consider the difference between using PLA while constantly staying on top of it, or just using something that is safe for a reef tank—such as PETG or PET—then the ultimate choice becomes clear.
ABS and PLA materials are too much of a mixed bag to bother with when there are better options out there. Once again, that’s not to say that you can’t use PLA. In fact, there are probably a lot of PLA fans that will want to refute this article with every fiber of their being.
However, it still boils down to the same thing. Why use a potentially risky material, regardless of the low percentage of risk, when there are better materials available?
Does PLA Leach Into Water?
The PLA itself doesn’t leach into the water. The saltwater will break it down, but if anything leaches into the water, it’s the dyes that are used to color the PLA material. As the PLA material breaks down, the colors/dyes have nothing to hold on to and will leach out into the water.
You can always go with PLA and print something that doesn’t have any dyes in it, or take some extra time to research the printing filaments that you are using and make sure that it’s FDA approved and non-toxic.
If your heart is set on PLA, then you will have to use wax and fixative sprays to heavily coat your PLA material so that it won’t break down over time. In saltwater, without wax or fixative spray, your PLA, 3d printed model will degrade in about half a year’s time.
If there are several dyes in your printing, then they will leach out into the water as the material breaks down. Even if it’s non-toxic, you’ll have to break everything down, clean out the entire tank and refill it to get the material out.
What 3D Printing Material is Reef Safe?
PET printing material is considered safe for reef tanks and there are several versions of it, with one of the more popular PET materials including glycol, so it has a “g” at the end of PET for PETg.
PET is Polyethylene Terephthalate, and it is every bit as rigid as PLA. PET doesn’t break down in saltwater like PLA will, however, it is easily breakable. Perhaps not as breakable as glass, but you want to take care of the finalized product.
PETg is Polyethylene Terephthalate Glycol. It’s exactly the same as PET, with glycol being the lone addition to the formula. The glycol addition gives the finalized product a little more flexibility, so it’s not as brittle as standard PET.
Of course, this is all going in a reef tank so unless you have a Megalodon in there, they aren’t likely to break, whether you go with PET or PETg. PETg in particular is astoundingly resilient to breakdown, even in saltwater, and also happens to be one of the strongest filaments available.
How Long Does Saltwater PLA Last?
As mentioned above, PLA will last about 6 months, without any additional preventative maintenance involved, such as coating it in a protective material—which in itself can be problematic.
If you are going to make PLA last longer, you’re going to have to coat it in wax or use a fixative spray. So now you have to turn your attention towards locating wax or fixative sprays that are also non-toxic to saltwater life and won’t break down.
It’s not like you can melt Crayola Crayons over your PLA masterpiece and consider it safe for your reef tank. You will need to find something that is non-GMO and completely non-toxic. Once you have the right way, you’ll need to melt it down and coat the entire PLA object with it.
Outside of protecting the PLA material with something else, it’s not going to last more than half a year and, as mentioned above, you’ll end up having to clean up the entire tank to get the degraded material out of the tank. You’re better off just sticking with PET or PETg material.
PET and PETg material won’t break down within a six-month period, you don’t have to coat it, and you don’t have to worry about harmful elements within the filaments.