Ph Levels

[benthyer]

So I tested my tank water tonight to guage my pH level ready for when I set up my new tank as I plan on having shrimp in it.
 
To my surprise my pH level was 8.2, I don't remember it being this high ever! So I thought I would test my tap water as I have moved house since I last checked it but I haven't moved far at all, in fact I am only a stones throw away from my old house.
 
Upon checking the pH level of my tap water it came back as about 7.5, so now I am baffled as to what could be causing my pH level to rise by 0.7.
 
If anything I thought my pH level would drop as I have bogwood in the tank or am I misinformed? However I do have a lava rock in the tank and don't know what effect, if any, that would have on pH level.

 

[Byron]

First, we (you actually) need to be certain of the tap water test.  You should let a glass of tap water sit 24 hours before testing pH, as this will out-gas any CO2 which will affect the reading.  From your numbers, I would suspect the CO2 in the tap water gave a false test result (lower than the true pH level).
 
Second, aside from the above, any substance composed of calcium or similar mineral can raise pH.  Rocks and/or the substrate material are the usual candidates here, if either are composed of limestone, coral, shells, marble, dolomite, aragonite, magnesium.  I had thought lava rock might also do this, though I have read the opposite.  It might be worth putting a piece of the lava rock in a pail of fresh water and see if over a day or two the pH rises.  Obviously, do the CO2 out-gas of the water to ensure you know the actual pH first.
 
Third, other additives can sometimes raise pH, thinking here of some plant products.  But this is usually insignificant.
 
Organic matter such as wood, peat, and leaves will tend to lower the pH because they break down slowly, releasing CO2 which causes carbonic acid and this results in a lowering pH.  The same process occurs from the breakdown of any organics (like fish waste) in the substrate.  However, this lowering is somewhat kept in check by the initial GH and KH of the water.  The KH in particular acts as a buffer, preventing a change in pH.  This works up to the point when the buffering capacity is exhausted, which would depend upon the initial GH and KH of your tap water.  It is worth knowing these numbers, and you should be able to ascertain them from your water authority's website.  Generally speaking, we do regular (weekly) partial water changes that work to keep all this stable, preventing sudden fluctuations.  The pH is only one aspect of a very complex interaction within the water chemistry.
 
Byron.

 

[benthyer]

Thanks Byron for all the information. I will set a glass of water aside and complete the test again to get a true reading.

I have a normal aquarium gravel in my tank so not sure of the effects if any from that, but I have had this gravel since day 1.

I have added a new product to the tank this week for my plants, I don't have it to hand right now but will post what it is when I'm next near it.

I have found the water report for my area and you can see that here:
https/www.wessexwater.co.uk/postcoderesult/?postcode=Ba2%202ug

 

[Byron]

Your GH is on the hard side, so most likely the KH (Alkalinity) will be similar.  That means the pH will remain quite stable in the aquarium.
 
Your out-gas of the CO2 test will confirm, but there is little doubt in my mind now that the result will be the higher pH, which as I said previously will be more accurate.  With the buffering by the KH, this is not going to lower noticeably regardless of wood, etc.
 
I would doubt the substrate gravel is raising anything, assuming the out-gas test result is basically where the tank is in pH.
 
Byron.

 

[benthyer]

Did the test on my tap water after running my air pump in it for about 2 hours - TTA said it will speed the test up.
 
I can confirm that you were right as my test came back with a pH level of 8, slightly lower but might because the CO2 is not completely gone.
 
My concern now is that I will not be able to have shrimp becuase of the pH level, What are my options? And what would be the most cost effective solution?

 

[Byron]

Agitation of the water can out-gas CO2 as well, though (according to TTA) may not work in reverse, but you've confirmed that you have moderately hard water with a pH close to 8.  So the mystery is solved.
 
Shrimp should be fine in this.  They need the mineral for their exoskeletons, and I am not aware of a high pH bothering them, but if any of the members with shrimp experience say differently, go with them.  Fish would be of more concern probably.
 
Byron.

 

[benthyer]

See I thought Shrimp would be fine, because like you said, the minerals would help. However on my research so far most people are saying 6.5 - 7.5 pH and some of the shrimp soils I have looked at - becuase I thought I would need to lower my pH - say they will lower the pH levels to anywhere from 5.5 - 6.5.
 
I'll go make a post in the relevant section on the forum with regards to shrimp and pH levels etc.
 
Thanks for your help Byron!
 
P.S. Been informed that you are good with plants, may be pestering you again if my new plants all die off

 

[Byron]

In my view, if the shrimp will be fine with pH 7.5, they will not have issues with 8.  It is usually water softness and acidity (and more the softness) that causes issues.  May depend upon the species.