Aquarium rock expert opinions

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Uberhoust

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The rocks are sandstone. They appear to have been sculpted after being quarried by rock drills and likely a bit of sand blasting to give them smoother and more interesting shapes. Most sandstones have a mix of minerals that bind the sand grains. The flaking you see on the rocks suggest a calcite matrix holding the sand together. If your pH and KH have been normal with the rocks in the tank I wouldn't worry about it, these sandstones will flake from time to time as the matrix(cement) dissolves/corrodes. Also sandstone is porous so even algae growth on the surface may be a partial cause for the flaking. Finally because the rocks have been quarried and shaped you might have flaking occurring because of the internal stresses in the rock are equalizing.

If you want to test these rocks for carbonates you will have to expose, chip away, enough rock to expose an unweathered face. If not you may get a false negative result from your test. If most of the exposed carbonates have been corroded, there might not be enough of it remaining to affect your water chemistry between your water changes.

I have seen pallets and drums of this type of carved stone in Arizona, particularly Quartzite. The rock is relatively soft so it doesn't take long to drill a hole in it. It is sold by the pound whole sale, or at least the stuff I seen is, so I could see purchasing a drum of it mark it up 100% and selling it retail by the pound.
 
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autyfish

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The rocks are sandstone. They appear to have been sculpted after being quarried by rock drills and likely a bit of sand blasting to give them smoother and more interesting shapes. Most sandstones have a mix of minerals that bind the sand grains. The flaking you see on the rocks suggest a calcite matrix holding the sand together. If your pH and KH have been normal with the rocks in the tank I wouldn't worry about it, these sandstones will flake from time to time as the matrix(cement) dissolves/corrodes. Also sandstone is porous so even algae growth on the surface may be a partial cause for the flaking. Finally because the rocks have been quarried and shaped you might have flaking occurring because of the internal stresses in the rock are equalizing.

If you want to test these rocks for carbonates you will have to expose, chip away, enough rock to expose an unweathered face. If not you may get a false negative result from your test. If most of the exposed carbonates have been corroded, there might not be enough of it remaining to affect your water chemistry between your water changes.

I have seen pallets and drums of this type of carved stone in Arizona, particularly Quartzite. The rock is relatively soft so it doesn't take long to drill a hole in it. It is sold by the pound whole sale, or at least the stuff I seen is, so I could see purchasing a drum of it mark it up 100% and selling it retail by the pound.
Thank you so much. They’ve definitely been drilled with something to make the caves and what not. My PH has remained around 7, but I’ve got a better test kit coming. My apisto loves the cave and basically lives in one of them, so I don’t want to just take his happy place away when he’s already stressed. I think after my next water change with all RO water, I will check parameters for a while after and see if the rocks appear to do anything. Someone mentioned that they may be limestone, but they’re definitely not. We have oodles and gobs of limestone around here and it’s more chalky, gritty than that like sandstone. We will go back over to the store and see if we can find some caves in a more solid substance (we have one that is that is sort of blue/green) and if they do, we will just switch it out. They’re $1 a pound, so it’s not like we are out anything really!
 

Colin_T

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If you want caves for dwarf cichlids, get clay flower pots and cut them in half (from top to bottom) with a hacksaw. Then rinse the pots and put them in the tank with the cut side on the substrate.

You can also use pvc pipe, with or without an end cap, to make caves.

Someone on here made a tube from flexible hose and buried it in the substrate with the ends poking above the gravel. The ends were some distance apart and the fish would go in one side and come out the other. It was quite good. :)

You can make holes in limestone and sand stone by dripping acid on the rock. It takes time but slowly dissolves a nice hole through it. You can also use a masonry drill bit and drill a hole through it.
 
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autyfish

autyfish

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If you want caves for dwarf cichlids, get clay flower pots and cut them in half (from top to bottom) with a hacksaw. Then rinse the pots and put them in the tank with the cut side on the substrate.

You can also use pvc pipe, with or without an end cap, to make caves.

Someone on here made a tube from flexible hose and buried it in the substrate with the ends poking above the gravel. The ends were some distance apart and the fish would go in one side and come out the other. It was quite good. :)

You can make holes in limestone and sand stone by dripping acid on the rock. It takes time but slowly dissolves a nice hole through it. You can also use a masonry drill bit and drill a hole through it.
Back in my college days, I made my own aquarium rocks from black sand and concrete. They were awesome and did super well in my tank after I let them age a bit of course. I also drilled out rocks with a masonry bit. These days with 3 kids, full time jobs, and all the things, I decided to just buy. Got a good reminder of why I made my own rocks in the first place. Back then I had African cichlids, who in many ways were just easier. Starting off with these dumb worms didn’t help anybody. They all act so much better since the levamisole, although only 1 fish had a visible worms. But I want to get things optimized since the apistos have ich from the heater crapping out.
 

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