Well heck!!! It worked last night!
A quick Google search of "Gobies eat Zebra Mussels" produced this though:
Contaminants Transfer: On the positive side, round gobies eat large quantities of zebra mussels, another invader that is causing an increasingly large number of problems because of its huge reproductive output. As filter feeders, Zebra mussels, consume toxins that are found throughout the Great Lakes. Zebra mussels are an important component of the gobies' diet in their native range; and, in laboratory studies in North America, a single round goby can eat up to 78 zebra mussels a day. However, it is unlikely that gobies alone will have a detectable impact on zebra mussels. The round goby is expected to be one of several species (including ducks, crayfish, diseases, and other fish species) that eventually will reduce the abundance of zebra mussels. The concern about this fact is that Gobies are preyed upon by several sportfish species (e.g., smallmouth and rock bass, walleyes, yellow perch, and brown trout). Because the diet of round gobies consists predominately of zebra mussels, there may be a direct transfer of contaminants from gobies to sport fish, which could increase the health concerns about eating fish