Limestone rock, is it safe?

jonnyf84

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22 Mar 2009
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Hi, for my upcoming re-scape i would like to use local rock, i'm from Wensleydale in the yorkshire dales so up on the fells there is a fantastic selection of beautiful limestone rock, is limestone rock safe to use in aquariums for both plants and fish?
 

GreenNeedle

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Plants won't mind it too much unless your Ph is already very high. I've used limestone before (quite a large amount) to hold some wood down for 6 weeks. The tank had no fish in it so can't comment on any effect on fish.

Whilst it will raise the Ph there is a lot in the tank trying to lower it i.e. wood and CO2.

So whilst the CO2 and wood and other things are lowering the Ph, this increased acidity will errode the limestone quicker.

If you have fish then I don't know what effect it will have on them but it won't affect plants. at least not in the short term.

Why did I choose limestone? because it was what I had to hand with living in a limestone area.

There is about 5 kg of limestone here in 125ltrs of water. You can't see it all but there are 8 large pieces holding the wod down. It came out once the wood was fully soaked:
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AC
 

jonnyf84

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22 Mar 2009
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thanks fella's, i was aware that calcium carbonate in the limestone rock would raise ph and hardness however it shouldn't go above 8 which is generally fine and i presume this change would happen slowly so the decrease caused by co2 shouldn't be too bad, its more the fish i'm worried about as they are rare and difficult to get hold of.
 

jonnyf84

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22 Mar 2009
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bump, could do with some more info on this if anyone has any as my re-scape is only a few weeks away, i'm not too keen on spending £100 + on landscape rock.
 

Ed Seeley

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The answer you got from the two guys earlier really covers everything! It will raise your GH, KH and pH.

You say you're putting some expensive fish in. What are they and what conditions do they need? If they like soft, acideic conditions and you're prepared to use RO water to give them natural conditions then limestone would be a bad idea!!! If you're using tap water and they're fish that don't mind hard, alkaline water then limestone will be fine. I've just redone my tank with a schist that contains veins that were a limestone-type of rock but as it will contain Tanganyikan cichlids it will actually help keep the water conditions more stable.

You can effectively ignore changes in pH caused by CO2 - it doesn't seem to affect the fish. What you need to do is use a drop checker to keep the level of CO2 below 30ppm so you don't gas the fish though.
 

jonnyf84

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22 Mar 2009
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I'm more worried about the larger fluctuations in PH, at the moment it is ranging from 6.5 - 7.4 due to the CO2, but with limestone i'm presuming the fluctuations will be more like 6.5 - 8, this is a big difference.
 

Dave Spencer

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Many of us experience the kind of 24 hour pH fluctuations that you are worried about. This kind of change can generally be considered a non event.

If the limestone raises your KH, then your water will be buffered and pH changes will be reduced.

What fish are you getting?

Dave.
 

GreenNeedle

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jonnyf84 said:
I'm more worried about the larger fluctuations in PH, at the moment it is ranging from 6.5 - 7.4 due to the CO2, but with limestone i'm presuming the fluctuations will be more like 6.5 - 8, this is a big difference.
Indeed like Dave says Ph is not the problem. People warble on about Ph problems with fish when in reality it is KH that is the problem. KH doesn't change with CO2 realted Ph swings so the problem is a non event.

I have a lot of surface turbulence so my Ph changes from 6.2 to 7.2 within an hour or so of the CO2 switching off.

AC
 
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