Nerite snails: shell issues, what to look out for and potential causes

What to look for

Erosion or pitting — the shell looks dull, pitted, or like it's wearing away. Cracks or chips — damage that exposes the soft body. White or pale patches — can be old damage that the snail has partly repaired, or new erosion. Holes — in bad cases, the shell can develop small holes. If the snail is still moving, eating, and sticking to the glass, it can often recover if you fix the cause; if the body is exposed and the snail is inactive, the outlook is worse.

Common causes

• Soft or acidic water. Snails need calcium and carbonate hardness (KH) to build and maintain shell. Very soft or acidic water can dissolve or weaken the shell over time. Test your water parameters; if GH/KH are very low, consider crushed coral, limestone, or a remineralising product (used carefully so you don't shock fish).
• Lack of calcium in diet. Nerites graze algae and biofilm, but in very clean tanks they may not get enough. Some keepers offer calcium-rich foods (e.g. blanched kale, snello, or commercial snail foods with calcium) or a cuttlebone in the tank (remove the hard back, sink the soft part).
• Injury. Being knocked off the glass, trapped in equipment, or harassed by fish can crack the shell. Provide hiding spots and check that intakes are snail-safe.
• Old damage. Sometimes erosion or white patches were already there when you bought the snail. New growth at the shell opening will look healthier if conditions are good.

What you can do

Improve water hardness if it's very low; add calcium via diet or cuttlebone; avoid sudden big parameter swings. Keep water quality good so the snail isn't stressed. See our general snail health guide for more on what to look out for with snails.

Quick takeaways

• Watch for erosion, pitting, cracks, or white patches on the shell.
• Soft/acidic water and lack of calcium are common causes; support with GH/KH and diet.
• Protect from injury and keep water stable so the snail can recover if possible.