Rock ID

[Maylin2]

Does anyone know what kind of rock this is? My husband believes it is a type of limestone as it reacts to acidic substances, but I don't have any idea what type it is.

This is an old photo of a bare bones sump piece before I added it to the tank.

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[Curtswearing]

It looks a lot like Holey Rock (honeycomb limestone). If so, it's usually used in Cichlid tanks because the pH of it is good for the cichlids.

 

[vikubz]

I used some of that for base rock in my tank. Now it is totally coated in coralline and is indistinguishable from the other LR.

 

[estanoche]

I used some of that for base rock in my tank. Now it is totally coated in coralline and is indistinguishable from the other LR.

Agreed - Texas Hole-ey Rock - Many people convert it to live rock in SW tanks, but most use it in Cichlid tanks...... I did too back in the day It should be harmless, and excellent base rock!

 

[Darthv247]

limestone = bad for reefs. will lower ph as it degrades in the water. Not sure if that is limestone though.

 

[Herefishyfishy]

Respectfully, Limestone acts more as a buffer and if anything will raise PH. Grind it up and it makes Kalk powder. The extra minerals could be suspect though.

 

[Maylin2]

Thanks for all of the wonderful input. It googled the stuff and that seems right on the dot. Vikubz, you're right on about the coraline algae. I had some cool serving plate sized pieces I put in my display and it looks like any other really porous coralline covered rock at this point. Good to know it's safe, lol.

It makes one heck of a natural frag rack too...

 

[returnofsid]

I also agree that limestone is good for the reef, not bad. As it slowly dissolves (only at low ph) it buffers, which in turn, raises the pH. A rock that size would take many many years to notice any visible effects of the dissolution.

My only concern is that if it is terrestrial rock, there's a possibility of other minerals within the rock.

 

[Herefishyfishy]

My only concern is that if it is terrestrial rock, there's a possibility of other minerals within the rock.

Better that than being extraterrestrial, really bad to get alien infestations

A majority of limestone is generally considered reef safe, and can be a great addition but not as good as reef rock for filtration due to a lack of porosity.

 

[Maylin2]

What other minerals should I be concerned about?

I'm not sure if I understand the porosity issue. Does that have more to do with the composition of the stone than the shape of it? I tried to look it up and got pw = Mw/V to o = Vo/V which means nothing to me, lol.

 

[Herefishyfishy]

Reef rock is like very bubbly lava. Water can permiate right through the solid rock. Gives a vastly larger surface area for nitrification and even a bit of denitrification inside.

The limestone you have is much more solid with big holes. Great for decoration and does add to the surfase area some.

The minerals would be natural ground precipitates. The metals would be the only concern but not much to worry about unless you swa some bad indicators in the tank.

Google limestone mineral composition for some idea.

 

[Maylin2]

I'll have to do more research on this, but thank you.

Would you happen to know what a bad indicator would look like if it was caused by released metals?

 

[returnofsid]

Depending on how long it had been in your tank, if it started releasing metals, you could have corals, snails, other inverts, dying or showing signs of stress. Another indication would be "rust" colors, or stains, appearing on the rock, as it leaches metals and those metals oxidize.

 

[Herefishyfishy]

Michael is correct. Most of limestone is Calcium, Magnesium, and Carbonate. It is remains of million year old reefs. It in itself is 100% safe. The concern is what it mixed with in the ground. The brown color is either clay/mud or could be iron/ manganese, etc. Very few minerals are of any real concern. Copper, zinc, and heavy metals. These would create different colors yet in the rock. If it was mine, I would soak it in vinegar or very dilute muriatic acid to leach out the free metal ions. Then rinse very well and it should be 100% safe. These rocks are very popular with the freshwater cichlid keepers and other fresh water fish. It dissolves slowly in freshwater, would be neutral in the high PH we keep our tanks. If algae grew like crazy or corals would not grow or open, take it out. Base rock (dead live rock from the ocean) can be found pretty cheap if patient.

 

[Maylin2]

Well, all corals/inverts are fine. My concern is that I would confuse the rust, if it appeared, with coralline algae, diatoms, or cyanobacteria. Thank's for the head's up though.

 

[Herefishyfishy]

If all the corals and inverts are fine, then simply enjoy your pretty rock :>)

 

[Maylin2]

Will do... And i'll be keeping an eye on it too. I would hate to soak it at this point, considering the abundance of life that now resides within/on it, but I'm glad to know there are options. I'll keep that in mind though when I have to move the tank this fall/winter and if I'm noticing anything of concern by then.

Thank you all for your help

 

[Darthv247]

well the slate limestone in minnasota was great for low ph tanks like south american chichlids. sorry for the confusion