I've been gathering rocks which I will eventually bolt together to form natural looking caves and crevices for my corydoras riverbank biotope. I'm wondering if there are any rocks that I should avoid that will adversely affect the water or might release toxic metal compounds into the water.
I got most of these rocks at a local stone yard that sells rocks by the pound for landscape designs, custom fountains, stone wall construction, and driveway gravel. Most of them look as though they were in water at some point as they are smooth, but a few have small sparkly elements in them that I worry could harm the cats. Thoughts?
Stones that release metals into water are pretty rare - heavy metals are even more rare, as they are quite unusual in nature. Anything that has "gold flecks" (fool's gold) in it should be avoided.
If you have soft to medium hard water, and don't want it to go harder (corys generally prefer soft water), you should also avoid stones made from calciferous rock - test with vinegar - if the stone bubbles, it's calcium carbonate, which will make your water harder and increase the pH. But if your water is quite hard already (and much of Florida has VERY hard water), it won't make much difference.
Some of your stones look like granite, which is definitely fine. A few others look like slate, which is also absolutely perfect. The ones at the right end of top and bottom rows look suspiciously like calciferous rock, so worth a check.
None of the rocks bubbled at all when I placed acetic acid on them (one of the many benefits of having a biochemist wife) so I seem to be good to go on that front. I am going to bolt and/or silicone the rock formations together and place them on top of my bottom layer of substrate (flourite or something similar) and then pour the sand layer around them so they're rooted. The rocks are mostly small so I'm thinking I'm not going to shatter the glass
I would also use styrofome to protect the bottom glass. A note of caution, if you do silicone the rocks together, if in future you need to remove these rocks, it will become difficult if you have 6-7 rocks stuck together. good luck and post a photo when you have finished cheers jk
I am not perfect, but I say as I see it. Smile and enjoy Life
Now you are asking - I do remember having read on this forum that in the USA it is often coated, but not always. You should ask for uncoated, or unprotected styropore
We only have pure styropore in NL, but that does not matter to you in the USA.
@ bolting together, I've been piling stones for over 220 years now, and I never bolt anything together. In my eyes, that makes the work of remouving the stuff far too heavy. I use rock wiith a langth of at least a third of the tank height as a basis framework, later adding smaller rocks
As an example, later this morning I'll be pulling the rocks out of my 400 * 100 * 70 cm high tank, and many of tham are over 30 cm long - the heaviest is 40 * 30 * 30 cm approximately. The tank needs redocorating and the insertion of inside filters