From this NASA [pdf](https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20110015764.pdf):

> At 46:40:02 Mission Elapsed Time during the Apollo 13 mission, both
> oxygen tank fans were powered on, hopefully to get a more accurate
> reading of the tank pressure.

In fact, the pressure is not influenced by fan operation. The reading of the capacitance tank gauge depends on a constant temperature of tank contents.

[![enter image description here][1]][1]

> 56 hours into the mission, at about 03:06 UT on 14 April 1970 (10:06
> PM, April 13 EST), the power fans were turned on within the tank for
> the third "cryo-stir" of the mission, a procedure to stir the oxygen
> slush inside the tank which would tend to stratify. The exposed fan
> wires shorted and the teflon insulation caught fire in the pure oxygen
> environment. This fire rapidly heated and increased the pressure of
> the oxygen inside the tank, and may have spread along the wires to the
> electrical conduit in the side of the tank, which weakened and
> ruptured under the pressure, causing the no. 2 oxygen tank to explode.
> This damaged the no. 1 tank and parts of the interior of the service
> module and blew off the bay no. 4 cover.

Image and quote from [this](https://nssdc.gsfc.nasa.gov/planetary/lunar/ap13acc.html) NASA page.

> Through the first 46 hours of the mission, telemetered data and crew
> observations indicated that the performance of oxygen tank 2 was
> normal. At 046:40:02, the crew routinely turned on the fans in oxygen
> tank 2. Within three seconds, the oxygen tank 2 quantity indication
> changed from a normal reading of about 82 percent full to an obviously
> incorrect “off-scale high” reading of over 100 percent. Analysis of
> the electrical wiring of the quantity gauge revealed that this
> erroneous reading could have been caused by either a short circuit or
> an open circuit in the gauge wiring or a short circuit between the
> gauge plates. Subsequent events indicated that a short was the more
> likely failure mode.
> 
> At 047:54:50 and at 051:07:44, the oxygen tank 2 fans were turned on
> again, with no apparent adverse effects. The quantity gauge continued
> to read off-scale high.

From [this](https://history.nasa.gov/SP-4029/Apollo_13a_Summary.htm) NASA page.

So the fans were activated to mix the supercritical fluid oxygen to get a uniform temperature and uniform density for a better result from the capacitive filling level probe. Previous readings were above 100 %.

As Organic Marble mentioned, the tank stored neither gaseous nor liquid nor solid oxygen. The oxygen was in another state, the supercritical fluid.

  [1]: https://i.sstatic.net/VLA8a.jpg