I certainly agree with your that shrimps are a good addition to freshwater tanks. I don't believe ghost shrimps (Palaemonetes paludosus) breed in aquaria because they have larvae offspring, but many other shrimps will breed freely, including the excellent cherry shrimp (Neocaridina heteropoda). Crayfish are fun in some ways, but the aren't community animals, and I think it's worth mentioning that they'll also eat aquarium plants. They're omnivores in the wild, and will really eat just about anything. Now, clams are where I really disagree with you. They don't live in freshwater aquaria: they merely die slowly. At least (marine) giant clams get some of their nutritional needs via symbiotic algae; freshwater clams are entirely dependent on plankton they filter out of the water. Moreover, the most commonly traded clams are coldwater animals, and in tropical tanks quickly die anyway. The standard tropical clam is Corbicula fluminea, and while hardy in the wild, its lifespan in aquaria is minimal. Avoid. Snails are great! I agree with you there. But I would recommend against the standard apple and mystery snails. They don't live for more than a year in aquaria because of their need for a "resting" phase once a year. Maintenance is do-able in specialist set ups that allow them to become dormant for a few months, but why bother? There are some excellent freshwater snails out there. Nerites are universally plant-friendly algae eaters without parallel, provided you get freshwater rather than brackish water species. They don't breed in freshwater tanks though, since their larvae are planktonic. Tylomelania spp. snails are also excellent, and at up to 12 cm/5 inches long, really impressive animals too. They're somewhat carnivorous, and like catfish pellets, krill, and the like. Cheers, Neale