Can I use crushed coral?

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11 Sep 2018
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I'm about to totally start again with my 60ltr. aquarium that is well established because I've found planarai and also fancy a change of style after 3 years. I have pygmy corys, octos, cherry shrimp and tetras. To get a new visual effect my daughter has offered me some crushed white coral from one of her chiclid tanks, but I'm not sure it would be suitable (I was personally thinking of using black sand) I've read conflicting items on the net about it's effect on the water chemistry. Is there anybody who has used it in the same set up I have who can vouch for it, or advise against? Here is the set up as it is today. Thanks

IMG_3433 2.JPG
 

Tim Harrison

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My advice would be to find a more inert alternative. Crushed coral will be high in carbonates and will undoubtedly raise TDS.

However, that said I used coral sand way back as a cap over peat. I lived in a hard water area so perhaps it didn't affect the water chemistry too much, and the peat will have absorbed some calcium ions.

The tank was low energy and I got incredible growth from plants like vallis, swords, Aponogetons and Crypts, but that's not really surprising since those species can synthesise carbon from bicarbonates.
 

tiger15

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14 Mar 2018
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I have kept African cichlid for years and converted the tank into planted tank a few years ago. I inherited dolomite gravel as substrate, not crushed coral per se but CaMgCO3 rock that can raise pH and gH. But since I do weekly 75% water change and inject CO2, pH approaches my tap water and has never gone above 7.6 pre photo period. My plants are thriving and I never have the need to dose gH.

Ca and Mg are macro nutrients and thriving plants will consume gH. I am surprised not more aquascapers use alkaline substrate as unlimited source of gH.
 

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tiger15

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14 Mar 2018
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Crushed coral is very abrasive, not great for your corys to rummage in.
True. This is why I chose dolomite over crushed coral because I don’t want my cichlid to dig into sharp grains that hurt their mouth. Another of my objection to crushed coral is that it dissolves faster and turns water dusty and milky when disturbed. Im really speaking about the chemistry which I don’t see a problem as many folks live in limestone/chalk area and can grow plants. I actually introduce limestone rock in my other planted tank as a reserve for gH, better than dosing.
 
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