• Get the NEW AquariaCentral iOS app --> http://itunes.apple.com/app/id1227181058 // Android version will be out soon!

Crushed coral is a problem waiting to happen


It's me
A lot of lfs try to sell us crushed coral to use as a substrate in our marine tanks. It's not good it acts as giant nitrate factory and really causes some long term issues with your tanks health. You would be far better served if you would use sand or even a bare bottom.

There are several reasons that it causes problems like, it catches all the detritus in your tank, food, feces, dead plants etc. It's more or less like having a kitchen sponge in the bottom of your tank that you never change! :thud:
Your infaunal critters be they fish,inverts etc. have a very difficult time in moving through it and they can't get to the waste material to eat it.

It also won't compact enough to form an anaerobic area to allow denitrification and the ultimate removal of waste as atmospheric nitrogen. In short it's not a good idea to add to marine tanks in quantity.

IME it probably causes more people to leave the hobby than any other reason!

Hopefully other members will post their experiences to assist new hobbiest.
Last edited:


It's me
I hope people will add more to it lol. Thanks for the vote of confidence guys!


AC Members
What is the propers process of removing the crushed coral from a tank, especially if already set up with fish and live rock. Is it possible to catch the fish and move them to a temporary tank for a few days and get rid of the CC. Will this cause a good deal of shock? And how long will the "sand storm" last?


It's me
The sand storm will last for a day or a little less just turn off your power heads. You'll want to renmove you fish and rock to tubs ,"with aeration and heat!" Fish in one and rocks in the other. Drain the tank of remaining water and put in your sand,"leave an area mostly clear of sand to rebuild your reef on it's much more stable on glass!
Get a glass bowl and refill tank turn your power heads back on.
When your water is starting to clear again replaice the fish and rocks. There shouldn't be much shock just test your water to see if you have a mini cycle and do water change if needed. Don't worrry about some sand in the water column anytime there is a storm in the ocean it's much worse than you getting rid of your cursed er crushed coral.


AC Members
You guys are right on the money. The matter that was building in my cc has caused my nitrates to spike. That is probably why my snails died. My fish are ok, but I am starting the process of removing the cc. I also went to my lfs and purchased saltwater inorder to do a water change of 15%. My nitrates have been decreasing and I plan on adding a soft bed of live sand.



The Old Guy
Crushed coral is solid now

I tried to remove the crushed coral and it has solidified and won't be removed unless I hit it hard with something. This is an old tank (18 years old at least) and with my luck I'll have a disaster on my hands.

Is it feasable to add enough sand to fill the spaces completely and eliminate my nitrate sponge substrate?


AC Members
to be honest crushed coral isnt all as bad as it is made out to be it realy does have its advantages for some tank set ups ..its only a nitrate factory if its not cleaned periodicly (syphoned).


It's me
The only tanks imho that benefit from a c.c. substrate are ones that don't have fish. It would be very difficult get enough material out of the bottom of it to have any good affect.
Tom, if it's solidified due to ph reactions over the decades it probably has enough of
an anoxic area to serve as additional live rock! I'd have to say that's a new one for me.