Hole in shells

[MrWolf]

Hello,

since few weeks, I noticed holes in some of my hermit crab shells. I tough it would be my water parameters, maybe ph too low or not enough calcium but this is my parameters:
ph: 8.4
Alk: 8.4dKH
Cal: 425ppm
Mg: 1380ppm
No2, No3, NH: 0

What can cause these hole in shells?
I also got one shell with scratch on it.

Link to picture

 

[Peach02]

only thing I can think of is a shell dwelling tank 'mate' but I'm not aware of many in the reef keeping hobby so I'm not sure. What do you have in your tank currently livestock wise?

 

[MrWolf]

only 2 clownfish, 1 cleaner shrimp, hundreds of snails and few hermit crabs
I also have 1 bristle star

 

[Peach02]

only 2 clownfish, 1 cleaner shrimp, hundreds of snails and few hermit crabs
I also have 1 bristle star

some types of snails kill other snails but I can't remember the name type sorry. Look up shell dwelling snails

 

[MrWolf]

I think it's bee snail, but I only have trochus and nerite which are really safe

 

[Peach02]

I think it's bee snail, but I only have trochus and nerite which are really safe

not sure then only other thing I could imagine is them falling and landing on their shell

 

[MrWolf]

That happen really often. I didn't know the shell could break by falling from the rock.
i'll try to inspect my hermit more often to spot hole.

thank you

 

[Peach02]

That happen really often. I didn't know the shell could break by falling from the rock.
i'll try to inspect my hermit more often to spot hole.

thank you

I've never seen it ether but its the only thing I can think of apart from shell dwellers

 

[Squeaky McMurdo]

some types of snails kill other snails but I can't remember the name type sorry. Look up shell dwelling snails

Welks. They drill a hole in the shell. Not sure they would prey on hermits, but maybe?

 

[Unclemilty]

I have a clown and three hermit crabs and have the same thing happening to some shells... some of my thoughts are... 1. Crabs grow quickly and are always looking for a new home, after inspecting the same shell many times over many days/weeks/months, they may break a hole in it so they won't keep looking at a shell that doesn't meet their needs.
2. I often hear them clanging shells together very loudly and violently... not sure if it is a mating thing or a trying to take over another crabs shell thing. But I feel it is a mating thing as they are face to face and no one ever gets hurt. They must do this to the back of an empty shell to create the hole as it is violent and seems almost spring loaded when the shells hit together.