Hi All - First post (well repost with pics). Sorry if I inadvertently break any rules!😁 My question: I recently purchased around 10 MTS's which arrived healthy and lively. I kept them in an isolation tank with some Java moss for a couple of weeks while my new 20 Gal main tank finished cycling. For a week or so, these snails seemed SO happy! They even started reproducing after only a couple of days and were quite active, even in the day time. Then it happened. I tested water parameters one evening and found that I had a huge nitrite spike (2 - 5 ppm).

Some of the snails still seemed fine, others were sucked up into their shells with their operculum slammed shut. Luckily, my tank had finally finished cycling just the day before. So I immediately got all the snails out and put them in my main tank. As before, some seemed fine (last pic). Others not so much (first 2 pics). The unhappy ones appear to be snapped shut in their shells and are exuding what I believe to be an excess of mucus. I've read that they do this when they are extremely stressed. They have been this way for about a week.

I've confirmed that my water parameters are stable and all in the green for MTS. I even tested for copper - nothing detectable. This, along with the fact that other snails in the tank are fine, tells me it's not a water quality problem. So, I am wondering if these inert snails were just less tolerant of nitrite than the others? Maybe they're just stressed and will eventually come back out? Or is this what the "snail death process" looks like? I've given one of them the "sniff test", and it did not smell foul. So I think they are still alive, just dormant. Has anyone seen this before? Anything I can do to help them? Or are they "goners"?

Trumpet issues