Could the same effect be achieved by just eating foods that are hard to digest, like sweetcorn. Would save the whole microplastic thing and give the fish some food.

I less care about the effect on the body (idk if its good or bad) and more care about shitting out micro-plastics.

Mineral oil is what i was planning to use, it’s issue is that’s it’s pretty viscous so would need to be moved around mechanically. Some plastics are ok with ipa (can use other solvents)

Yeah it’s definitely a fire hazard, and just a health hazard in general. The pressure should self regulate, as it gets hotter it will increase pressure, which makes it easier to cool down. Would be in something metal that could take the pressure. And completely sealed so no air can get in all heat would have to conduct out.