Congratulations on controlling the snail problem! If they're out of other snails to eat then they go back to carrion if it's available. You may have to throw in extra shrimp pellets or similar sinking food to keep them fed. It shouldn't be too much trouble.
The TPWD is very clear that collecting what they consider to be bait fish is perfectly fine. Using traps is also acceptable as is seining. It's keeping game fish and invasives as pets that they have a problem with but if an officer is curious just make it clear that you're after minnows, darters, mollies or Gambusia and they won't mind one bit. They may even give you some helpful tips.
One word of warning, though: Travis county in general is home to a number of threatened species such as the fountain darter so make sure that you're going to a place that isn't home to a known threatened species or that you won't be collecting any by accident or uprooting their habitat. A little research will help you avoid a possible run in with the law or at least aide you in releasing an accidentally caught threatened animal. Otherwise, I think keeping native plants and animals is fun and educational so I do encourage it.