Where did they come from?

While cleaning my tank tonight, I noticed two snails on the glass near the surface. The larger was about a 5mm long.
That made me pay more attention, and I noticed at least a dozen more, mostly 2-4mm long, on the walls, filter, and gravel.



I found a lot of posts here and on other sites about how to get rid of these 'pest' snails - but I was wondering something else:

(1) Can anyone ID them? I'm just curious what they are.

(2) If I leave them, will they harm the tank? right now, the tank has 3 skirt tetras, a single angelfish, and a pleco. It's not a planted tank. Will they harm the fish?
- and could there be any possible connection to this: https://www.fishforums.net/threads/black-fungus.477719/

(3) Other than regular water changes (50% every 7-10 days), I have not added anything to this tank in more than 7 months. I'm pretty sure I last added fish in April-May, or possibly even earlier than that. The tank is not planted. Where could they have come from?

Hello. 1. Look like some sort of pond snails to me. There are many different species around the world, but they all behave about the same. 2. No, they're harmless, and can even be beneficial. They usually won't overpopulate unless you are over-feeding. 3. It is really hard to say how they got into your tank. Perhaps they've been in there since May, and you're just now noticing them. Some inverts can be very good at staying out of sight. Perhaps they are very slow-growing. Or perhaps they came in some way that you haven't thought of yet. Whatever the case, they probably aren't connected to the black fungus problem, and they shouldn't hurt anything.

I agree with Badger. They are harmless and helpful. Shouldn't be a problem unless they have too much food!

They look more like trumpet snails to me. These snails are know to burrow in the substrate, and since they are really small you might have gotten the eggs from somewhere and then they hatched.

Other then that I agree with what has been said already, snails are usually harmless, even tho unsightly. If you want to get rid of them, limit the feedings that way they won't reproduce as quick. Additionally, you can manually remove them or even get assassin snails, they will eat the snails and get rid of them completely.

nik_n said:

you might have gotten the eggs from somewhere and then they hatched.

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I got my answer of where they came from.

A few days ago, I went back to my local fish store, where I purchased some fish back in March - and found that almost all of their tanks were had these snails, some of them up 1cm long.

I chose a couple fish (I have the snails already, so I figured it doesn't really matter), and while the employee was bagging them, I commented that the store should really inform the customers that with every fish, they get some free snails. He laughed, and offered me poison of some sort, for free. I turned it down.

I don't see the snails often - they do seem to spend most of their time in the substrate - but I actually like the way they look. Unless they get out of hand, I'm just going to leave them, and if they do get out of hand, I would rather remove as many as I can manually than introduce more chemicals into the tank.