The issue with any wild animal is that they are loaded with parasites, and other bad guys - this also makes an issue for a tank (esp. with tank breed fish who have never been exposed to these illnesses). Many of these bad guys are kept in check by constant water flow and lack of nitrates/phosphates but in any home (read enclosed) aquarium these chemicals are orders of magitude higher so bad guys can go 'wild' (bad pun), that is multiply uncontrollably. Also, in the wild only the super healthy tend to live due to these factors but tank breed are not this healthy. Store bought is safer (most times.) Dr.fosther/Smith sells clams. Clams do not do well unless you can feed them properly and have very clean water (mature is not the issue) that is changed (mature just means you have a lot of nitrates that are kept at a modest level due to wc). My two cents and good luck.