pH advice

[Robbie_t]

I'm setting up a 250 litre tank. My water is currently about 6.0pH and quite soft. I'm planning on having south american cichlids, angel fish etc and think i'm best off with a pH of around 7.0 for the variety of fish I want. I am trying to give the tank a marine look, so was wanting texan holy rock and I believe this increases the pH and hardness.
My question is, would introducing a limestone like texan holy rock raise my pH to 7.0 or would it take it too high? Or does it depend how much I use?

 

[FishEggs]

i believe it does depend on how much you use in the tank. the best way to find out is to try a piece in a bucket of water and test the ph for a few days.
i had a large rock (not texas holy rock, it was a quartz with other minerals) in my tank at one time and it raised the ph to over 8 from 7.6.
every rock is different so i think you might just have to get the pieces you want and put them in the tank and do some testing.

 

[happygirl65]

I agree with Matt it is best to test it in a bucket for a couple of weeks.

But I would also like to add, that south american cichlids like discus, angels, rams etc like and thrive in the softer more acidic water so you really don't have to add anything unless your pH is unstable and bounces all over the place.

Also almost any fish can adapt to a pH that is different from the "ideal" conditions and thrive, the key is stability. If your pH fluctuates or crashes then you really do need to add a buffer of some kind but if it stays stable in the 6.0 range then you are all set already.

 

[jsoong]

You can't really "dose" rocks to get to a specific pH ...

Any carbonaceous rock will drive the pH towards equilibrium, in this case 7.8 or so (assuming there is no other buffer in the water). You can't really make the reaction stop at 7.0. <Unless you added a very small piece & the whole thing dissolved .... in that case the reaction stops when all the rock is gone.>

 

[Robbie_t]

could someone explain in simple terms what a buffer is? I've tried reading up on it but im no chemist and my mind starts to wander!

 

[happygirl65]

A buffer could be minerals that are already present or something that is added such as baking soda.

Often times raising your GH or KH (adding baking soda for example) will stabilize a pH that fluctuates or crashes.

So in simple terms a buffer is something that makes your pH more stable and usually raises the pH, GH and KH.

But I should add that some other folks might explain it better as I am also no chemist and have only experience with hard water that needed no additional buffering agent.

 

[HN1]

My question is, would introducing a limestone like texan holy rock raise my pH to 7.0 or would it take it too high? Or does it depend how much I use?

It really depends on quite a lot of factors including how much rock is added, flow, etc. Have you measured your pH after letting it sit out overnight? It tends to rise as the CO2 gasses off so you may have a higher benchmark than you think. I personally believe that it's far better to maintain a constant pH without adding buffers than it is to shoot for a particular number. Unless you are planning to keep wild caught specimens, angels and the like will be fine into the mid-high 7s. Just acclimate carefully. Most fish these days are farmed in various water conditions and have become quite adaptable.

 

[happygirl65]

Exactly! I raised angelfish from dime sized to larger than my hand in 7.8 pH and my water did exactly what HN1 described....started out at 6.5 then once the CO2 was gassed off it would rise up to 7.8 where it was stable from then on. I also kept discus at that pH and raised them quite large and healthy as well. Many fish (even so called sensitive fish) are adaptable as long as conditions are stable.

 

[jsoong]

In simple terms - a buffer is a mineral that is dissolved in water, which acts to resist pH changes.

All buffers are salts of weak acids. Eg. are carbonates, bicarbonates, phosphates, acetate (the "base" salt of vinegar) .....

I agree that it is far better to maintain a constant pH than a specific pH. In water without buffer (eg distilled water) this is difficult to do, so adding buffers is recommended.