Cabbage toxic to snails?

[InvisibleTouch]

I keep a number of species of common aquarium snails, and the other day I added some fresh cabbage leaves to two of the tanks. They eat just about everything else, I figured they'd love the cabbage. In one tank, the snails converged happily on the cabbage; in the other tank, they ignored it. The next day, 4 out of the 6 big snails who had eaten from the leaves were withdrawn into their shell, the other two were moving about, but not as active as usual, and very nervous - startling easily whenever I looked in on them. Entirely not like them at all, since these guys are normally lively and active (for snails). And they are my favorites, with their plump round shape and their long and elegant feelers, so I was quite worried about them.

I threw out the cabbage and changed the water completely, and eventually the 4 withdrawn snails came back out - but they're still not quite themselves, still not as active and confident as normal. (The 4 big guys in the other tank are the same as ever; they were the smart/less-greedy ones - but to be safe I totally changed their water too.) So, I know what I'm not feeding my molluscine friends again! I've since given them some halved grapes, which they like a lot.

Anyone else had this experience with cabbage leaves, for any type of pet? I did wash them well, so I don't think it was a pesticide residue, but you never know. I'm rapidly reaching the point where I'm unwilling to feed any vegetable matter that's not organic or home-grown.

[The Velveteen Ocelot]

1. Don't snails and slugs eat cabbage in gardens?

Maybe it gave them gas?

I have no idea...

[InvisibleTouch]

2. I think land snails do...

...but my guys are aquatics. Anyway, just thought I'd pass along the experience, if it can be of use to another pet keeper.