Everyone I know here in Columbus has trouble with snail shell erosion. I've looked at the water report but there's nothing unusual. It's kind of annoying because I really like the critters in my tank. If I drop Ca, they start dying off. It would be a big coincidence that suddenly something damaged their shells everytime I lower Ca.

I'm open to suggestions. It would be a huge breakthrough to figure this out.

Don't you even have problems with them reproducing, Reiverix? Or are they just not living long enough to do that?

I can keep a steady population if Ca is above ~60ppm. I've been thinking about some high calcium snail food recipes and see if that helps.

Diet might be some of it.
But it's not precisely clear, CO2 is more likely the cause although many species seem unaffected in naturally high CO2 systems in nature.

Regards,
Tom Barr

I'm pretty sure it's a pH thing. Snail shells are composed of CaCO3 like everyone else said, which dissolves into the water at a low enough pH. When I started my tank, I aimed for the KH ~ 4 and pH ~6.8 to get a good CO2 level and my ramshorns' (which seem to be more sensitive than some other species) shells all started taking on a white pitted appearance. I've since taken to adding some baking soda during WCs to raise pH above 7 and still maintain a good CO2 level, and while the old holes in the shells haven't healed, new ones haven't developed either.

A PH of lower than 7 can corode snail shells really fast. They really dont like acidic water. If your adding CO2 then its likely that your PH is going to drop below safe levels.

If I recall correctly, snail shells are not primarily calcium carbonate. They are, I think, mostly a protein. Most of us using CO2 with low KH have a pH below 7, without problems with snails, other than having far too many.

Interesting, this is something that Ive read in 2 separate places now, both on snail/invert supplier website. Im wondering if theyre just over-covering their backsides?

That does not sound completely accurate.
My understanding is that the snail shell is primarily composed of calcium carbonate but that there is a protective outer covering.
The outer covering of the snail shell is the periostracum, which is mostly protein.
Drop the snail shell in acetic acid and the dissolving calcium carbonate will form bubbles of CO2 as it dissolves.

And you are correct........

All FW snails and mollusc possess a protective layer, this prevents dissolution in the much more corrosive FW waters.

Now there are plenty of snails in natural systems with high CO2 waters.......there are tons of snails, I do mean tons, in pH of 4.7-5.1 in Florida, you can see them all over.

So why do the snails in our tanks get them holes?

The only good hypothesis I've got is damage to the layer, fish, transport, algae holdfast(see BBA after the alga dies, it'll leave a nice hole).

There are a number of things that will harm the layer.........but the pH and CO2 of tank itself is not part of it near as anything in a natural system could ever suggest....

If you accept that pH and high CO2 do cause an issue, why doesn't harm the snails where they are from etc?
That's going to be a huge hurdle to accept that hypothesis.
I'll say that CO2 ferts and low pH once the layer is busted is not helpful, but they should not be the primary reason.

Olive nerites I've personally collected from Santa Fe river, the pH there is 5.0.
Other locations had CO2 levels of 25 ppm, and the entire substrate was covered in a dozen species of snail, clams, FW mussles etc.

The hardness was very low and in some places, very high.
Snails everywhere.

Regards,
Tom Barr