quick question not realy an emergency

can i use limestone rock in a reef tank?

 

I would not recommend it. I will errode in time and chemically react with the water.

M

 

BTW, Limestone is actually calcium carbonate. Other may feel different, I'd just rather not add that variable to possible problems.

M

 

I think it's fine. I have always been under the impression that the rock we get from Fiji, Tonga, Marshall Islands, Florida etc. is just limestone or a form of limestone. You want the rock to react with the water. Carbonate based rock will help buffer the water if you have a low PH. Everytime people have asked whether they can use a type of rock, I"ve always told them use a carbonate based rock, not silicate. I could be wrong though, but I'm also pretty sure the rock I have in my tank, fiji rock, is carbonate based.

 

is limestone cheaper? if its carbonate based then go for it!

 

i feel wrong disagreeing with the guy who works at NASA... but i believe that the calcium carbonate is good. it buffers and slowly releases Ca in the water.
I have a fine limestone bed under my sand...

 

The terrestrially mined "base rock" everyone uses is calcium carbonate, aka aragonite, oolitic stone, or limestone

Coral skeletons are Calcium Carbonate, limestone.

Ocean sand is Aragonite or Oolitic sand - calcium carbonate - limestone.

It's not only fine to use, it's good for your tank.

Now that said... make sure it's limestone and something of a silicate nature.

-Doug

 

If you put in Limestone, you should get a (very slow) reaction of CaCO3 > CaO + CO2. CaO is quicklime, which reacts with H2O, giving Ca(OH)2. Ca(OH)2 happens to be called "Kalkwasser" by many in the aquarium hobby.

If you read about live rock, people reccommend replacing a percentage of it on occasion. This would be to make up for the depletion of live rock's buffering capacity. As the above reaction provides buffering capacity, I see no reason to shy away from limestone. Likely, it's what most people selling base rock are giving to you anyway, if they aren't giving you "ancient coral skeleton" type rock, which in itself is actually CaCO3, just not in as solid of a chunk as land-mined limestone.

You should seed the tank with a piece of real live rock, though, to get all the organisms you won't get on land-mined limestone.

 

I would be concerned with potential pollutants in the rock and also whether or not the rock is porous enough to provide a good surface for bacteria to colonize. It depends what sort of quantity you're thinking of using though and what other filtration you have on the system whether you really need the porosity.
There are such a huge variety of sources of limestone that I would probably be concerned mostly of some type of pollutant in the rock, even if it's just somewhere buried in the layers of the rock as the rock reacts with the water it might potentially get to a nasty spot and release something into the tank.

That might just be me being paranoid though. I would just go with dry rock from bulkreefsupply or something similar, it's pretty cheap and I believe is more safe to use just based on the fact that so many people use it all the time.

 

Freshly quarried limestone was formed hundreds of millions of years before there were people to pollute it...

But even if it looks solid to our naked eyes it is in fact very porous, so it CAN absorb pollutants over time. If it's been sitting on the surface for a number of years I would certainly be wary of it, and find a better source for rock.

As a filter, it's great. There's plenty of room for bacteria in the microscopic pores of even very dense limestone. Of course very dense limestone is heavy, and usually won't look very good in a tank. It could also takes months to fully saturate, since the pores are so small and would easily clog. All that would do it prolong any cycle it goes through. In the end it will serve as a filter.

If you can find travertine get some of that, it's got LOTS of bigger holes in it, and looks really nice as a baserock.

Of course nothing beats real live rock, and right behind that is "natural" dry rock, followed by terrestrial ancient coral reefs... but if it's all you have access to limestone is reef safe.