Matt wrote:Maybe the terra cotta pot has something to do with the drying out? I know that it's porous and evaporates the water quickly.
I'll bet that's the case. Growing medium in red clay pots dries out about twice as quickly as in plastic or glazed ceramic. It's possible to grow Venus Flytraps in real red earthenware clay pots that have been fired to maturity, because they are chemically pretty inert and insoluble. But there are very many imitations of true red earthenware clay pots that are actually very low-fired "ceramic bodies" that have lots of slowly soluble chemicals or minerals in them, so a person has to really know their clay, avoid those and be really sure that the clay pot is made of only red earthenware clay.
I'm growing a couple Fine Tooth x Red Venus Flytraps in a real red earthenware clay pot right now, and they're doing fine, but I really should have made the mix more moisture retentive to compensate for the porous red clay's tendency to wick water away from the medium and evaporate it from the pots outside surface.
There is not a tremendous danger of a buildup of minerals and other dissolved solids when using real red earthenware fired to its maturity (until it almost is ready to melt in the kiln) if both the water and the growing medium used are very low in soluble material. A quick scrub and rinse of the outside surface of the clay pot is good enough to remove any visible "bloom" of minerals left on the surface as the water evaporates.
Stoneware clay pots are fine to use. They are vitreous (non porous) if they are fired to maturity, and are as good as any glazed ceramic pot. However, lighter colors might be better, to keep the sun from heating the pots and the growing medium and roots too much.
Good luck and best wishes--