Plastic is pretty stable. Since this is an aquarium it isn’t get direct sunlight at a rate to make the plastic degrade to the point of polluting the water.
Also, since it’s an aquarium, the are already many kinds of plastics involved. The pumps, tubing, filters, and so on all contain plastic that would have a heater likelihood of degrade sure to mechanical action.
that does make sense, though I just assumed that those would be made with proper precautions/use suitable plastics
wasn’t sure whether 3d printed filament is on the same lvl in terms of that, hence my original comment
Reef tank owner here. People who make these use a type of plastic known to not degrade and become an issue. All is good!
Most plastic (not all, but most) is good to go. It’s metal you have to worry about. Or lotion on people’s hands / makeup.
If something is bad for a reef tank, you usually find out pretty quick with quick deaths. The ocean doesn’t tolerate contamination or fluctuations of anything - it likes things very stable…
