Hitch hiking snails?

June 29, 2013 8:25 AM

We have a fish tank (freshwater). We had two yellow apple snails, they died. Last weekend I found two large brown snails in a local lake. We added them to the tank. Now we have two large snails and at least 15 identically-sized small snails (just under half an inch or so in diameter). Where did they come from?

The new snails cleaned the heck out of our (kinda grungy) tank, which is nice - but we thought we were getting two snails, not a baker's dozen and then some. The small snails look just like the large ones - brownish, your ordinary Midwestern freshwater lake snail. The large snails are pretty big, about golf ball sized. I picked the snails up out of the water and put them in a container when I brought them home - noticed at most 3 small snails in with them when we arrived. All 15 small snails look like those three in general size and shape. So they didn't all just hatch in the tank since last week, or they would be different sizes - the little ones are pretty uniform. And none of them are yellow. We had small brown snails in the past, and when new ones hatched we could see them even when they were really small, so I'd think I would have noticed these if they were hatching from eggs laid by our now-departed yellow snail friends.

So where did they come from? I have never heard of baby snails hiding inside the shell of larger ones, but... Where else could they have arrived from, if not hitching a ride? And I'm sure I would have noticed 15 little snails hanging on to the outside of the large ones! We don't have any live plants in the tank, and it was snail-free for weeks before adding the new ones in last Sunday...

posted by caution live frogs to Pets & Animals (9 answers total)

They're common pond snails and they reproduce like crazy.
posted by bradbane at 9:13 AM on June 29, 2013

So they didn't all just hatch in the tank since last week, or they would be different sizes

Why would that be the case? If they came from the same clutch of eggs, wouldn't they all be about the same size?
posted by showbiz_liz at 9:15 AM on June 29, 2013

Did any lake water come in with them - even a bit? There could have been eggs in that. Even so, they fertilize their own eggs.
posted by peagood at 9:37 AM on June 29, 2013

I meant since I know there were at least 3 small snails initially, and all 15 are the same size... They shouldn't be from the same batch of eggs, unless they all came in together in the first place. Just curious if it was possible that they were hiding inside the larger shells.
posted by caution live frogs at 10:36 AM on June 29, 2013

There are several kinds of small loaches (e.g. Botias) that will eat small snails. They generally won't bother with the larger ones. Bear this in mind when your current 15 smalls snails become 500.
posted by pipeski at 10:45 AM on June 29, 2013

Had this happen when I bought two snails years back. I soon had a "snail tank" instead of a fish tank. Snails breed like rabbits (or maybe rabbits breed like snails . . .).
posted by anansi at 11:43 AM on June 29, 2013

Snails are hermaphroditic. They, um, mutually reproduce each other (in slow motion). So, I guess each of your original snail pair can be the father/mother, aunt/uncle to a bunch of cousin/sisterbrothernephewnieces. After that first generation, the family tree gets complicated.

Their eggs are tiny. I usually found them attached to water plants, sometimes to the underside of floating objects in the tank.
posted by mule98J at 11:46 AM on June 29, 2013

I believe that iron-based algae killers will take out invertebrates if you want to try that (don't do it if you have shrimp!). Other than that, in my own planted tank that has 3 different populations of snail species I sometimes drop in a piece of cucumber (or whatever) and then pull it out when the tank is dark. That usually gets rid of a lot, but you'll probably never get rid of all of them.
posted by bradbane at 3:23 PM on June 29, 2013

These are baby snails.

Snails can store their fertile eggs inside their bodies for a while before laying them, and can also be super sneaky about hiding the clutch- I know because two days ago I suddenly had a ton of bitty baby snails and I had no idea that my snail had lain a clutch! Baby snails will hang out in the clutch eating their egg shells and getting big and strong before they start exploring; I'm guessing that's what happened here.

PS, cute snaily pics please? They are pets after all!
posted by windykites at 4:35 PM on June 29, 2013