This creature is a waterdweller that somewhat resemble a fish. It lives in the retreating oceans of a planet orbiting a star that is reaching its red giant stage. The planet is now experiencing very high levels of radiation and life is becoming extinct...

The creature is a photosynthetic animal so it needs to live close to the surface of the oceans but they lay eggs at the bottom of the oceans to protect their youngs. The youngs eventually develop a strong armour once reaching maturity and lose their fins.

The grownups are basically rocks, they do not have the ability to move any appendages since their thick and solid exoskeleton. They have the ability to move around thanks to a bio-MHD

in the bioMHD the electric current is passed thanks through stacked cells like those of an electric eel.

How can I generated the magnetic field to push the water through?

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    $\begingroup$ This is kind of cop out, but you do not really need magnetic fields. You can move water with electric fields. Or more precisely, if you have electric charge beneath an insulator, the ions contained by sea water will respond to its electric field. If you then move the charge, the ions and water will also move with it. $\endgroup$ – Ville Niemi Jun 2 '16 at 10:18
  • $\begingroup$ Maybe the armor can be made of some Alnico alloy(Not sure how they could develop this) and the current produced from the animal can pass between the armor and skin in a given direction to move it? $\endgroup$ – Timmy Jun 2 '16 at 19:18
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    $\begingroup$ The energy costs seem way too prohibitive to be feasible in a gut check. These things eat what besides sunlight? $\endgroup$ – The Nate Jun 3 '16 at 13:36
  • $\begingroup$ Maybe they only have to move occasionally? Float near the surface and use ballast to change depth and only move in short bursts when necessary. Why would a photosynthetic organism in the ocean need to move anyways? Can you explain the purpose of their movement? $\endgroup$ – Mike Nichols Jun 3 '16 at 14:34
  • $\begingroup$ @TheNate they do not eat anything, their mouth is sealed, in the last stage of their life they go on only with sunlight which they use to continuosly produce ATP-like molecules. They don't need extra material since they don't grow anymore $\endgroup$ – SilverCookies Jun 3 '16 at 21:41

You just need a source of magnetic rock.

If you will read in Wikipedia, you will see that many minerals and, well, stuff is built into exoskeletons already, by organisms on our good old Earth. Some (like iron sulfides greigite and pyrite) using metabolic means, others (grains of sand) are added by simply sticking them on.

Use both. Make some iron metabolized into youngling's skin, and then magnetic sand particles will stick to it and grow in when skin thickens into armour.

Other way is to "simply" use electromagnetism. Coils are pretty common in body design, just make them conductive. Electricity you have.

Actually, I'd use both, because permanent magnets deteriorate over time. With added bioelectromagnets, organisms could "recharge" them and stay mobile longer. Unless magnets failing is your designed way of death of old age, of course.

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    $\begingroup$ Technically, you can recharge permanent magnets in much the same way as they fail: Instead of sucking the potential energy out of them by having them create a field, you put them into a stronger field. Intensity and temperature both matter and that's a bit of a simplification, but an organism could conceivably remagnetize stuff. $\endgroup$ – The Nate Jun 3 '16 at 13:43
  • $\begingroup$ @TheNate yes, I meant electromagnets to refresh permanent magnets. Wasn't clear on that at all... Sorry. $\endgroup$ – Mołot Jun 3 '16 at 17:42
  • $\begingroup$ I think your edits improved things. $\endgroup$ – The Nate Jun 4 '16 at 4:02

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