Big one fish tank setup

Does anyone have a marine set up suitable for a periwinkle snail my daughter thought was simply a pretty seashell And is able to collect from Hemel? I've checked and they don't asexually reproduce Just want to give this guy the best chance at survival but my fish tanks are freshwater

Anyone got a decent size tank they don’t want or going cheap plz

So the pond is filling up at the moment, and I’m going to leave it like this for two weeks or so. So I need a PH kit is there anything else I need before putting koi or gold fish in the pond

Want this but need to get the tank dialed in first