I guess too but why worry if it is a nice, quality ceramic pot? Haven't such things and water sort of gone together for millenia? I would never seal both sides of ceramic piece for the reasons you suggest.
You can try sealing it but if it oozes I suppose but you deny it the clay its quality of life and it will not last long I fear. You may find that once the water swells the clay shut it will be just fine.
Otherwise, and no offense, my a clay piece better fired and with denser structure to be used as a fountain.
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