But the indigenous Lionfishes of the Georgia coast need company!
Personally, I never flushed/released/etc any animal, even if it was dead. My standard practice was to leave it in concentrated bleach until it dissolved then wash it down the drain to ensure that whatever killed it didn't live to tell the tale.
In the case of clams, much as it pained me to see their dead shells in my tank, the bleached shells of my dear departed (I lost 6 clams to the epidemic Todd referred to) make great frag surfaces and aquascaping materials. Especially good for stopping sand erosion from powerheads, too.
