Slate Cave Rust Patches

[scobie140]

I just purchased a set of four breeding caves made from slate off ebay, these were intended for my L333 tank wich also houses cherry shrimp. Upon closer inspection when i was washing them to put them in they have lots of little patches of rust. I know cherry shrimp are very sensitive to copper so will these be no good as the iron i'm assuming will also poisen then. annoyed with my self as i had left positive feedback before giving them a good inspection. so untill i find out if the caves are safe or not then they arn't going in the tank. Thanks for anyone who can shed light on this

 

[Hermithall]

You might be right to show caution, go with your gut feeling and if you're worried don't put them in. The "rust" patches could be the mineral pyrite (iron sulphide) which can form on slate - also known as fool's gold which sometimes looks just like rust. Check the info and also the pic out on this site to see if you can verify anything : http/www.cichlid-forum.com/articles/rock_metals.php - Pyrite is gonna be deadly to Cherry Shrimp.
The only other thing I can think of is this: could the ebayer have made these from old roof slates? The tile pins could have corroded and simply stained the slate with genuine rust, which might just scrub off. Long shot I know! Ebay eh, you win some you lose some.

 

[scobie140]

I've had a scrape at them and its definatly engraned in the slate. The link isn't working just now but i'll try later. Looks like I wasted my money. I have messaged the seller but don't know what will come of it. Looks like its back to the drawing board for getting a load of caves for their tank. Glad you backed up my doubts, Cheers

 

[scobie140]

This is what the seller messaged me back.

the patches are naturally occuring not rust patches!!!! Been using the same batch of slate for 2 years and no reports of any fatalities and my crayfish have loads of babies. You have no need to worry. If you dont want the caves return for full refund.

Its not really worth me sending them back as postage is half the cost of the product. are crayfish as sensitive to metals as cherry shrimp? being honest unless anyone on here has had this and its been ok i'll prob just throw them out.

 

[Hermithall]

It's a tough call - but if he's telling the truth I guess it's reassuring. Other than pyrite (fools gold) I can't find any info on what else it might be. Here's the scare factors for pyrite:

1. It has a strong acidifying effect, i.e. it drops the pH.

2. In addition to iron it sometimes contains small quantities of other more dangerous heavy metals such as lead, zinc, and copper.

3. Because it acidifies the water it can 'unlock' heavy metals into their toxic free-ionic forms.

What's the guy's feedback like? Trawl through his FB and see who else bought his slate for their tanks - maybe you could message these other buyers to see how they got on with it.

 

[StandbySetting]

If it is actually rust then it will be fine as it isn't water-soluble, and nor is pyrite so how it has an effect on water acidity is mysterious, can you quote a source that claims that it will acidify water and that it is actually soluble? Smell it, if it smells like sulphur then it is probably pyrite. Quite a lot of slate I've come across appears to have rust in its layers, most of the time it's just other sediment that has been compressed under pressure whilst it is forming.

 

[Caprichoso]

This is what the seller messaged me back.

the patches are naturally occuring not rust patches!!!! Been using the same batch of slate for 2 years and no reports of any fatalities and my crayfish have loads of babies. You have no need to worry. If you dont want the caves return for full refund.

Its not really worth me sending them back as postage is half the cost of the product. are crayfish as sensitive to metals as cherry shrimp? being honest unless anyone on here has had this and its been ok i'll prob just throw them out.

I have black slate with that on it. I never actually knew what it was but since it couldn't be scrubbed off I didn't worry about it. It's been in my tank for years with no known adverse effect. I have shrimp as well.

 

[scobie140]

[/quote]

I have black slate with that on it. I never actually knew what it was but since it couldn't be scrubbed off I didn't worry about it. It's been in my tank for years with no known adverse effect. I have shrimp as well.
[/quote]

Well its been fine for you then i'll give it a try with the smallest bit first. I can see where Hermithall and standbysetting are both coming from. All his feedback from the slate caves are positive so must just be me being paranoid. It has no smell to it so thats put my mind at ease. I can cope with loosing a few shrimp but would be gutted if i lost any of the L333's so will just add them slowly and keep an eye on things. I like to be overly cautious when it comes to my fish. Thanks for helping to cear this up i'll let you's know how i get on

 

[Hermithall]

...can you quote a source that claims that it will acidify water and that it is actually soluble? Smell it, if it smells like sulphur then it is probably pyrite. Quite a lot of slate I've come across appears to have rust in its layers, most of the time it's just other sediment that has been compressed under pressure whilst it is forming.

Good question, pyrite is indeed an insoluble mineral but will nontheless acidify the water thus (you gave yourself a massive clue with your smelling sulphur tip):

The chemistry is as follows. Oxygen (and natural bacteria) in the water would oxidize the sulphide component of pyrite to sulphate (i.e. sulphuric acid). The lowered pH acidic water produced could then potentially activate the iron and any other heavy metals present. Don't put fool's gold (pyrite) in your fish tank!

 

[StandbySetting]

That's a fair enough chemical analysis, but it's a pretty easy compound to identify by smell and appearance, rust doesn't smell sulphurous, any luck OP?

 

[Juggler75]

Am I being stupid here? but could you not just buy a 25kg bag of large decorative slate from B&Q or something and silicone your own caves. Out of the bag you should be able to get some caves you would be happy with. e.g.

Do they need to be perfectly flat?