Basalt & Iron: Hardscape

Von Bronze

New Member
Joined
16 Jun 2019
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UK
Hi there,

I'm new to the forum and currently embarking on my first aquascape!

I'm keen to collect my own hardscape locally and many sources state that basalt is a safe, igneous rock for aquariums.

However, basalt was formed from "magnesium and iron-rich lava"

Some of the same sources will say that you need to avoid rocks with metal, or metal ores. Some pieces I've collected do have patches of iron oxide on the surface. See photos.

Does this mean that the online sources are wrong to list basalt? Or does it just mean a lump of ore is bad but surface iron/iron content is okay. I'm aware iron is sometimes added as a nutrient for plants.

Any advice would be amazing and much appreciated!

DSC02950.JPG
DSC02949.JPG
 

ceg4048

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Chicago, USA
Hello,
Basalt will be fine. There are sediment products such as Caribsea's Eco Complete which are reportedly basalt based. Iron Oxide will also be fine as this will provide Iron for plants. For many years, Laterite clay sediments were prized for their Iron Oxide content.

The sources which caution against using metal ore containing rocks do so as it is unknown which ores are present and to what extent these metals are present in any given rock sample. So for example, the Iron, which is visible, is a good thing but there may be other, undesirable metals, such as Cadmium, for example, which you'd wish to avoid.

We dose very small amounts of metals, such as Iron, Zinc, Copper, Magnesium and so forth in our micronurient mix, but these are known quantities. Without knowing the origin of a rock, or without a chemical analysis there is no way to guarantee the absence of toxic substances. This caution applies to any material placed in the tank.

Cheers,
 

Simon Cole

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25 Dec 2018
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469
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Buckingham
I've used basalt extensively due to it's rich mineral content and microscopic structure. I use basalt crushed, rock dust, and whole rocks. My father is a geologist and we regularly go collecting, so if you could mention the quarry/location then I'll get him to look into it.
 

dw1305

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7 Apr 2008
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nr Bath
Hi all,
I agree with the others, it will be absolutely fine.
Some of the same sources will say that you need to avoid rocks with metal, or metal ores.
This would really only apply to quartz etc with iron pyrites deposits or slag from metal working etc.

Have a look at <"Large rocks for large tanks">.

I use a different approach to looking at the suitability of rocks to most internet sources. I just go on how hard they are.

This is particularly useful with <"water worn rocks">, if it is a rounded cobble it is OK to use, whatever the parent rock was.

cheers Darrel
 

Von Bronze

New Member
Joined
16 Jun 2019
Messages
13
Location
UK
Thanks so much for the advice!

Ceg4048 - Great knowledge - spot on, and really helpful.

Simon - I collected these fragments from the foot of Dumbarton Rock - there is an exposed face used by climbers behind the castle. There wasn't a huge selection of loose rock at a carry-able size so I'm considering also seeking some gabbro from further North as well to use alongside (if it works visually). If you've been collecting in these parts and know of a good location or quarry with interesting, aquarium-friendly stone I'd be keen to venture out. Doesn't have to be basalt, could make the scape from something different like schist.

Darrel - Thanks for the links and the tip on hardness. Interesting to see in the second thread that one of the posters was able to find very affordable landscaping slate at a garden centre. Looks good and not too dissimilar.
 

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