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Nerite snails dying? near death ? or just sleeping?


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Hello all,

I am having some concerns over my 2 Nerite snails and wondering if there is some serious problems that this community could help shed light on.

I have a 50Ltr fresh water Aquarium, Water temperature is about 25 - 25.5 degrees celcius. The 2 Nerite snails share the aquarium with 6 Corydoras and 5 Ember Tetras and live plants such as Java ferns


For about 2 weeks after the snails were introduced to the Aquarium, I was amazed by the sheer speed they moved at and their insatiable appetite for the green Algae growing on the glass. Everything seemed to go fine and then I introduced some plant fertilizer to the aquarium to help promote plant growth, shortly after this, two things started to happen:

1: Brown furry algae started to appear on the rocks and some of the plants (not all) and increased green Algae in general

2: Nerite snails stopped eating, 1 went into hiding in between 2 rocks initially (in what looked to be an awkward position where I thought the snail may have become stuck) and the other simply stopped moving but remained fixed to the glass.

Following what started off as frenzied snails with an insatiable appetite the snails just seemed to not move and not interested in eating, I put it down to 3 possibilities.

A: Water parameters (so I tested for Ammonia spikes and the test came back as 0 ammonia, 0 Nitrite and 10 - 20 PPM of Nitrates (acceptable for plant life)

B: Temperature, temperature is about 25 - 25.5 c (77 - 77.5 degrees F) which seems to be okay

C : General hardness seemed to be about 13 Gh there abouts.


Following the observations of both the algae and the slow / lethargic movement of 1 snail + the immovable other snail, I firstly moved the snail that was "stuck" between two rocks, putting it into an observable location at the front and facing down (so as to not be eaten by the cories). The snail did eventually move, to the back glass of the aquarium. Where I later found the snail on its back and the snail receded completely into its shell where it still remains for the past 3 days.


The second thing I did was that I carried out a 20% water change 2 days ago, thinking that maybe the water parameters may be off (too much iron??)

Following the water change, 1 snail (the snail which receded) has remained unmoving and still in its shell this time turned facing down and the other snail remains on the glass, showing some life but with a white string coming out of it.


From reviewing blogs and the video linked below, I am uncertain, it seems its possibly parasites? if possible, I would like to get an idea as to what I should do next


Huge thanks in advance.


I have watched this video


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What's your PH, do you think they're getting enough calcium? My snails started doing better/living longer when I added cuttlebone to the tanks. 

Don't know about the white string - can you post a pic? 

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The white string may be poop. Can we see a picture?

Do you know what type of nerite you have? Some of mine are more active than others. 

What I think is most likely is that your snails had been nearly starved between the supplier and the store and were gorging themselves in your tank that has plenty of food for them. And now there's just napping.

My black racer snails do this the most. I'll see a ton of algae dissappear over the coarse of a few nights and then it slowly builds back up as they take a nap for what seems like forever.

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I've had trouble keeping nerites, but you should know I'm a total newb.  All I can do is share my experience and listen for any good advice.

My first online/shipped order of nerites were put in my tank 12 weeks ago.  3 zebra nerites and 3 horned nerites.  Today, I only have 2 of the horned nerites left from this order.

My second online/shipped order was put in my tank 2 weeks ago.  4 types of large nerite, and 3 zebra horned nerites.  I only have 1 batik nerite and 1 zebra horned left.

All of them performed like yours, at first voracious eaters and then they just stop.  I have seen them stop for a day or two and then start eating again.

Before I lay them to rest, I gently poke them to see if they react, and smell them.  If they react, I put them back in the tank.  If they smell like feces, they are laid to rest.

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If you worry about whether they are dead, dead snails do start smelling quite fast. You can smell test it, if it smells bad in a level it makes you gag, it is dead.

I had a chance to keep 6 nerites until today,3 zebras and 3 horned ones. I have never seen mine taking a nap in their shell. I usually find them remaining on glass or plants but never fully into their shells, they just like to keep themselves on glass but a lil bit burried into subsrate part or between driftwood pieces in my experience.

You never know if your water has calcium unless u specifically test for it or you dose/add something that has calcium intentionally. I use equilibrium and my snails all do fine! The best way to understand is observing day1 shell and current situation of the shell if it is getting enough minerals, if you have no time to kit for it. Your hardness might be coming from all different elements and maybe 0 calcium. You never know.

Also can you see their antennas? Some fish tend to see these as worms and may pick on them. Loss of antennas can make snails depressed in a level they don't move and die gradually. Also if they fall behind, they may get picked on as they don't have a trapdoor, and it can again get them depressed and killed. This is beyond if they can correct themselves tbh. More like, do fish let them to correct themself meanwhile.

Also, another thing that comes to my mind is, nerites don't eat every type of algae and only loves to graze biofilm and some type of algaes in my experience. Consider them like ottos or hillstream loaches. If your tank is new, or there is so many grazers on limited amount of food, they will starve to death. I've never seen them eating blanched veggies, snellos, wafers or fish food of any type. Make sure they don't starve.

These are my experiences

Edited by Lennie
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On 2/7/2023 at 4:21 PM, MattyM said:

What's your PH, do you think they're getting enough calcium? My snails started doing better/living longer when I added cuttlebone to the tanks. 

Don't know about the white string - can you post a pic? 

Hi Matty, Perceptive and Katherine,

Thank you for the responses.

The last reading of the PH was roughly 7.6 with a small margin of error, I did not do a High PH test. In regards to calcium, not sure, if there was an actual proper method to determine calcium I would absolutely give this a try. The shell seems to be fine and intact. I also didn't notice any odd smells when I investigated the snail up close (specifically referencing the snail which receded into its shell), as I heard that a sign of a dead snail was either a sulfur or at least smell especially bad however this is not the case for me.

It is worth noting that on Sunday 5th Feb, concerned that maybe calcium or some other minerals were missing from the snails diet I went to the local pet shop and bought "bottom feeder" food, similar to the Hikari Sinking wafers, since I suspect that snails are bottom feeders and I have cory's then it wouldn't hurt trying, the particular food i bought included spirulina as I recall the video mentioning that, I didn't notice any of the snails feeding off the wafers, the corydoras seemed to like it though.

The below is a record of my water parameter readings and the dates in which they were taken, the N/A is predominantly times I simply didn't record GH and KH but as you will see below, the test results seem remarkably consistent and show absolutely no Ammonia or Nitrites and in my limited knowledge it shows a reasonably cycled tank, many of these results were recorded at roughly the same time during the evening so as to avoid throwing unwanted variables into the mix, I am acutely aware that these are basic water parameters and don't disclose stuff like Calcium or other minerals, which may affect the fish or snails.

10th Jan 7.2 N/A N/A 0 0 20
11th Jan 7.6 19 4 0 0 20
14th Jan 7.2 (or 7.6) 13 -14 3 0 0 10
16th Jan 7.4     0 0 20
19th Jan   13 4 0 0 20
22nd Jan N/A N/A N/A 0 0 10
24th Jan 7.4     0 0 20
31st Jan 7.4 13 4 0 0 10
4th Feb 7.6     0 0 20

I will work on getting those photos asap, i am bit tied to my pc at the moment so the photos will be a work in progress.

Edited by Yambino
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So here are the photos. I hope some of this is visible. I suspect I may have to walk you through this and explain especially the snail with the white thing trailing from it.


The first picture is the better one and give the clearest view of the snail which has receded into its shell, the shell looks clean and intact without any identifiable breaks or cracks at any angle, however hopefully the image speaks for itself. The green algae on the glass does not help with the mobile phones focus unfortunately.


In the second image I have provided a wider view of the aquarium to encompass the positioning of both snails and to demonstrate the scale of the Brown algae growth which came about not long after the fertilizer was added to the water for the plants over 1 week ago.


The final image is poor quality and understandable difficult to decipher even for me, the person taking it. However the contrast in color between the snails shell and this trailing white "string" should be visible. From my research, on similar topics elsewhere some people have speculated that this white trailing thing is most probably a parasite, however I open the door to those who have experience.




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On 2/8/2023 at 12:37 PM, Yambino said:

he fertilizer is: Tropica Specialised Nutrition

Kinda related, kinda not. But;

I don't understand that much from fertilizers. Two days ago, I've also ordered tropica specialised nutrition online, as my flourish was sitting at the end of the bottle and I wanted to try something new.

When I got the bottle and read the back side, it directly says ammonium. I know they market the specialised version for low bioload but very densely planted tanks, but I could not be sure how okay it is to dose ammonium into the tank with a water change. Does anyone have an idea about this? Especially in high ph, would this end up being toxic as ammonia or remains as ammonium? Wouldn't it be like dosing something toxic to tank intentionally?

Anyway, I refunded the specialised version and decided to buy premium version instead. That one does not have ammonium if I'm not wrong. But I'd love to hear about ammonium in all in one fertilizer and if it is okay for fish/snail/shrimp in the tank. This may also help you to get an answer I bet.


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On 2/7/2023 at 4:21 PM, MattyM said:

What's your PH, do you think they're getting enough calcium? My snails started doing better/living longer when I added cuttlebone to the tanks. 

Don't know about the white string - can you post a pic? 


I checked on my aquarium this morning and noticed that Snail 1: Still had not moved from the shell it receded to

Snail 2: While it had this white trail coming from it, was still very much alive and moving around until this morning where it fell off the glass (either via harrassment or other reasons) and has now gone into recede mode as well)


While Snail 2 has just decided to hide in its shell, I have taken it out and given it a smell check, there was no notable smells, however I pulled snail 1 out and smell checked it and it smelled like going off fish, so I have disposed of it, I also noticed some additional white stuff which seemed to be stuck initially to snail 1 prior to pulling it out of the water, I couldn't find the white strand like thing after it fell back into the water.


I have decided to treat the entire aquarium with API Melafix. While I suspect Melafix wont address what I suspect to be parasites, I do hope that dosing the Aquarium for the next few days will help, or at least isolate the problem to the snails, whatever the problem is. As a side note, Aquarium Co-Op does supply medicine like Fritz Paracleanse however I live in Europe and I have never seen Fritz products supplied here. So I will need to source parasite meds on my side.

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