I don't know if the nutritional value of ramshorn snails has ever been tested since people don't eat them, do you?
Giant land snails, however, have been tested, since they are looked at as a source of available animal protein for people with protein deficient diets in Nigeria. Giant land snails feed on plant growth and here is some of what was found:
"Concentrations of zinc, iron, manganese, magnesium, calcium, phosphorus, sulphur, potassium and sodium in the flesh of the snails were determined. Values of iron, magnesium, calcium, phosphorus, potassium and sodium were consistently high while cobalt, copper and lead were not detected. Snails complement the required trace and minor elements needed for proper growth and development in human being, so it is recommended for regular.
The current report provides information on mineral elements which compared favourably with the reported values of some lean domestic livestock meats as reported by Bender (
1992). Favourable nutrition elements are reported for protein, fat, phosphorus, sodium, potassium and magnesium. Consumption of giant land snail is therefore recommended for both old and young, as this will combine effectively with other food components in providing the required essential elements to the body.
consumption."
And here is the nutritional value of snails that we consume as escargot:
http://www.fitday.com/WebFit/nutrition/All_Foods/Fish/Snails.html.
We don't rely on escargot as the source of our daily nutrition, but they do add somethings that the body needs.
And in the same line as what I stated, not relied on for complete nutrition. I never see my loaches feeding on an algae wafer although they are added to the tank regularly for the cories. They do scarf up bloodworms and are fed bloodworms daily.
There's got to be some nutritional value in the snails when added to their regular diet, just not to be solely relied on as is the case with feeding all of our pets....furry and wet alike. Just my humble opinion on the matter.