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.
Waffle House, Denny's, IHOP, aren't even fast food... They're just bad food. I still don't understand why people eat at these places. It's not like it's ever the only option, or the cheapest option.
Also I love this picture.