Here's why:
* Leeches are aquatic worms: They lay their eggs in moist, protected environments, like under rocks or logs in the water.
* Rocks themselves don't contain leech eggs: The eggs are deposited by adult leeches.
* Introducing creek rocks can bring in other organisms: You might introduce other aquatic life forms like snails, insects, or even microscopic organisms, but it's unlikely to introduce leeches unless they were already present on the rocks.
If you're concerned about leeches in your fish tank:
* Inspect the rocks thoroughly: Look for any signs of leech cocoons or young leeches.
* Quarantine new rocks: Before adding any rocks to your main tank, keep them in a separate container for a week or two to observe if any creatures emerge.
* Be mindful of the source of your rocks: Avoid collecting rocks from areas known to have a high leech population.
Remember, leeches are a natural part of many aquatic ecosystems. While they can be a nuisance in a fish tank, they're generally harmless to fish.