Aquarium Decoration (Rocks, Plants and Substrates) • Any geologists in the house (marble scape?)

[Kagia]

I recently found a deposit of travertine/tufa, and upon closer inspection, found what I'm all but positive is a small deposit of marble metamorphic rock.

I've gone back a couple times to collect a bit for a new mbuna tank I'm setting up.

The rock has some greys and golden browns through it, which I've read may be caused by impurities in the limestone during metamorphosis.

Would this rock be safe for my fish, or could the impurities contain anything harmful to the fish?

Thanks.

[Deeda]

Pics aren't working for me.

[Kagia]

Hmmm...It looks good on my end.

I'll try again.

[noddy]

Looks like you struck gold : )

[Deeda]

I can see the pics now and the rocks look just fine to me.

[Kagia]

Thanks.

I'm worried about the composition though. I read on one website that it may contain impurities like pyrite and iron oxide, which I'm guessing might not be good for the fish?

[rolf.miles]

Maybe it would be nice to find the geological composition for the places where your cichlid is from, so then finding similar rocks seems to me a pretty safe way to go.

[Auballagh]

Those are good looking rocks!
As for the impurities you mention? I don't believe they will be much of a problem. If you place those rocks in a very soft water, acidic PH tank (Black water biotope), the water chemistry could react with and oxidize any metals in the rock. And, the lower the PH of your aquarium water, the more reaction you could possibly get between those rocks and the water (Geeeze... battery acid?!!!). But, even in a lower PH water aquarium environment, this is something which may - or may not - be much of an actual problem because of a couple things,
- Water changes to dilute Nitrate buildup, will also dilute any suspended metals oxidized from the rocks. The level of oxidized metal buildup may never reach levels that are a problem in the tank.
- Bio-slime, Diatom and Algae buildup. All of those things will coat those rocks in the aquarium, slowing down (not eliminating) the rate of potential metal oxidation from the rocks.
-
Now, if you plan on using de-chloramined municipal/city water to fill your tanks with, like most of us do? You're already several steps ahead of any problems. Municipal/City water is purposely treated to increase the PH. That is, after the disaster of Flint, Michigan, no one wants to be responsible for providing acidic PH public water, that leaches the lead out of old service pipes and causes water toxicity problems!
So, if you plan on using those rocks to build and stack up in a high PH water Central American, African Lake Malawi or Lake Tanganyika biotope? Those rocks will definitely work out just fine in there.

[Kagia]

Thanks for the reply.

I'm hoping to add a bunch of this rock to my mbuna and petricola tank.

Our city water is actually acidic and has zero hardness. I add a bunch of buffering agents (Malawi Buffer, Cichlid Lake Salt, baking soda, and epsom salt) to my water before I pump it into the tank for my weekly water changes.

I'm very torn here. I really want to add this rock to the tank, but not if there's any chance it could adversely affect my fish.

[DJRansome]

I would add it. No worries.

[Auballagh]

I think those rocks are gonna work out just fine for you in your African Rift Lake, Mbuna & Petricola catfish tank. It'd be a shame to waste 'em. They're great looking and won't hurt a thing in that aquarium. Use 'em!!
-
On another note....
Why does just about EVERYBODY have to fight the water they're given naturally for their aquariums? I looked on in wide-eyed wonder at the lengths you are going to raise the hardness and PH of your municipal tap water. I mean - Wow.
Do you know how many folks out there who are so invested in these crazy, Reverse Osmosis filtration water systems and other expensive gadgets to try and drive their own freshwater supply down to almost zero hardness and acidic PH?
Amazing. You have what appears to be a natural, almost unlimited supply of water that is just about perfect for building a New World, Black Water biotope aquarium. Something that is pretty rare, and is extremely cool to see in the aquarium hobby!
Oh man... there are just so many beautiful, hard to keep cichlids that just absolutely thrive in soft, acidic water conditions. Altum Angelfish, Discus, Uaru Cichlids, Satanoperca Eartheaters... and so many more, that so many us just can't keep successfully because of the naturally hard, higher PH water we are supplied with.
Oh well, to each his own I suppose.....