What setup would you recommend?

[richiem]

Using a "wall-wart" type AC to DC power supply is a good solution for powering the DC fan. You can run it constantly, or wire the AC side of the supply in parallel with the heater if you use an AC heater. I would choose the latter.

As my statistics professor used to say, "Life isn't ideal." DC is rarely pure DC unless A) it is a high-capacity battery source, or B) it is a source that is extremely well-filtered. Consider the DC power in a car -- the battery provides essentially pure DC, but the charging system generates time-varying fields due to the AC to DC conversion (ripple) of the alternator, and the various motors and switching systems all contribute varying fields. So what looks like a clean DC environment is a "polluted" one on the basis of time-varying fields. The case of the DC tank heater is much like that of the car because of the large currents required, which make effective filtering difficult and/or expensive. It can be done, but it isn't cheap.

Big batteries make pretty effective filters, so powering the DC heater from a battery stack that is located relatively far from the tank, with the batteries being charged by a relatively low-ripple AC to DC converter (or possibly an automotive battery charger) will probably best meet your needs.

I appreciate your desire to have a "clean" environment for the tank -- I've used an isolation tank several times, and was surprised by the experience of heightened sensitivity.

[Kanefire]

I really appreciate this perspective... It brings a lot of things into clarity.

To reiterate what you are saying...

The transformer that would convert AC to DC wouldn't create a "Pure" or "Clean" DC Current. This would be a relatively smaller issue with a smaller current, but since a 24V will produce a current of 27a+ the amount of current will still create some Time-Varying Field. Is this an accurate understanding?

If this is correct, then it would seem that it would simply come down to the numbers. What intensity of field would be created by this DC set up vs. a comparable AC system and does the price/trouble provide enough benefit to be worth it.

This almost brings me back full circle. My original idea to create a "clean" floating environment was to use a PEX radiant heating system. This was a bit more complicated as it would require pumps and heaters, but creating a clean environment is very important to me.

[richiem]

Not sure about relative field strengths -- a bit above my pay grade. Would really need to measure.

[Kanefire]

Yeah, I figured it would be a complicated comparison... I have been looking into PEX (radiant water heating) and it is looking to be much more complicated...

Anyways, a lot to digest. Thanks for your help.