Limestone Rock?

[BeerShark]

Okay went for a dive today and noticed that most of the rock that had corals and sponges living on it in my local area was limestone, (newby question) would having limestone rock (small pieces) in a tank be bad?

 

[Donya]

Limestone is fine IME (with a few catches), and I even cured some particularly porous limestone to use as LR. It's working great so far. One thing to be cautious of though: if you get the rock dry, keep the it in a bucket of water for a few days and monitor the pH. If it goes down sharply, you've got a "bad rock". This a problem I first heard about from freshwater folks who were using the rock ornamentally and as a pH buffer. Every now and then there are things in limestone that can cause pH to go down...sulfides, trapped tree root bits that decay (a problem for "holy rock" limestone), other hidden things, etc. If the limestone has marine beasties growing on it though, I think it would probably be free of that risk.

 

[SkiFletch]

I agree, if it looks the part (covered with coraline and other growth) and you can get it underwater quickly, limestone should be fine.

 

[BeerShark]

On the topic of rock, i got alot of really interesting looking brown sandstone from along the coast, thin flat sheets with holes all through it where its eroded faster, i dunno if the brown colouration means its heavy in some other element like iron or something, dads had simmilar bits in the freshwater tank for years, but he guppies in that tank are tough as nails( took 40 of them from alice springs in a big bucket in the trailer through the desert, bout 2 days and only lost 2 by the time we hit kangaroo island). i understand the term porous, im unsure if ive ever seen porous limestone rock anywhere, all the stuff i see underwater and along the coast is fairly rough with stuff growing on it but nothing like the stuff in LFS's thats much lighter and deffinately porous. is there much problem with using rock that isnt porous to seed the tank? even if i removed it at a later date maybe.

 

[SkiFletch]

Well, the difficulty with non-porous rock is that there are no anaerobic zones of water in the center of the rock to house nitrate eating bacterium. You'll therefore rely on other methods for nitrate export to keep levels down in your tank. Maybe some macro algae, or a DSB depending on what size tank you're going for.

 

[crazyelece]

All types and varieties of rock are porous, some just more so than others. Any rock will work as biological filtration mechanisms. The more porous the rock the more efficient it will be. Any calcium based rock (limestone) will work in a marine environment as base rock. Just remember the less dense (more porous) the better. A popular limestone around here for base rock is lace rock. It has a similar texture to live rock, is calcium based, and easily available.