"NetMax" wrote in message ...

Sorry to post on myself, but if someone knows German, this site had a bit
of info on them. Similar snails from the Neritas Genus (from a post from
Mean_Chlorine earlier this month), were quoted as preferring harder water
(14gH), but those I could translate.
http://www.wirbellose.de/arten.cgi?a...show&artNo=085

Neritids are primarily marine snails, although some species are found
in brackish or even fresh water. Also, they have thick shells, and
thick-shelled snails tend to live in water where there's plenty of
calcium.

The species I have, the european Theodoxus fluviatilis, is one of the
relatively few real freshwater species in the family, and even it
prefers hard, alkaline, water, preferrably with a little salt in it.
(I'm currently writing a text about my experiences with T.
fluviatilis, I'll post a link here when I've finished.)

Regarding N. natalensis I have no personal experience with it, but the
author of the species fact-sheet at www.wirbellose.de says he rotates
his snails between a brackish and a freshwater aquarium.