Weird PH levels.

So over the Christmas break, I set up a little 2.5 gallon shrimp tank for my sister. I used Flourite Onyx Sand, a bit of Lava rock, and an unnamed moss type. I replaced the normal carbon pad the build in filter came with with a Fluval ceramic bag, and the biowheel with a cut down filter sponge for some mechanical filtration. Due to not knowing exactly what was in their tap water, we bought store spring water to make sure we didn't have any copper issues.

The bottled water had a PH of 6.4. However, when we filled the tank and tested it, it's clocking in at 7.8 or so. What could be causing such a huge spike?

My guess would be there are/were deposits in the lava rock that are leeching into the water. Also what is your water hardness? If your hardness is low your subject to fluctuations.

Honestly I don't know. I assume the spring water will be relatively soft, so if it is the lava rock that would make sense.

Good way to know for sure is to pull the lava rock, and change the water. If the PH holds for say 3-5 days then you have your culprit. To my knowledge the Flourite shouldnt raise the PH if at all. My only other thought is maybe the moss? Peat Moss is generally accepted as a good way to slightly lower PH but your issue is it is increasing

Yeah, going to have her pull the rock for now and see what happens. It's more of a Java moss (don't know the specific species). If nothing else, have them swap the rock for a bit of mopani.

mvrck wrote:So over the Christmas break, I set up a little 2.5 gallon shrimp tank for my sister.  I used Flourite Onyx Sand, a bit of Lava rock, and an unnamed moss type.  I replaced the normal carbon pad the build in filter came with with a Fluval ceramic bag, and the biowheel with a cut down filter sponge for some mechanical filtration.  Due to not knowing exactly what was in their tap water, we bought store spring water to make sure we didn't have any copper issues.  

The bottled water had a PH of 6.4.  However, when we filled the tank and tested it, it's clocking in at 7.8 or so.  What could be causing such a huge spike?

Hi mvrck,

My tap water changes PH over the first 24 hours after it comes out of the tap.  Why not take a little of that spring water from the bottle, put it in a glass in the open air for 24 hours, and see if the PH changes?

Also, Seachem Onyx Sand typically raises the PH .1 - .5 per Seachem which does not account for all of the change you saw but may account for some of it.

Onyx Sand Product Description

Onyx Sand™ is a naturally dark gray sand that perfectly complements and enhances the appearance of any aquarium. It provides not only iron and other minerals but supports optimal KH levels for freshwater planted aquariums. Being carbonate rich, Onyx Sand™ provides an advantage to any plants able to utilize bicarbonates. Although ideally suited to planted aquaria, it may be used in any aquarium environment. Onyx Sand™ is most effective when used alone as an integral substrate bed, but it may be mixed with other gravels. Gravel modifiers such as laterite are not necessary. Onyx Sand™ is not chemically coated or treated but does have a slight buffering capacity that may raise pH by 0.1 - 0.5 pH units (depending on source water characteristics). Onyx Sand™ is good for the life of the aquarium and need not be replaced.

Seattle_Aquarist wrote:My tap water changes PH over the first 24 hours after it comes out of the tap.  Why not take a little of that spring water from the bottle, put it in a glass in the open air for 24 hours, and see if the PH changes?

Bingo! I'm willing to be that this is the biggest contributor. As the water off-gasses CO2 and 'settles' to say the least, the PH will flucuate. This usually isn't really that big of an issue, as the TDS level will usually remain the same. And I'm willing to bet that bottled water has little to no buffering capacity either.

EDIT: Here's a good link that kinda explains the relationship between pH, CO2, kH, and TDS/GH. [You must be registered and logged in to see this link.]

bronzefighter wrote:

Bingo! I'm willing to be that this is the biggest contributor.

I would not use any water that RAISES PH by 1.4. Fluctuations are ok but worst I have ever seen normal water do is .3. I am not saying that it is not the case. Just saying a PH flucuation of 1.4 from water settling seems a bit extreme.

Chiisai wrote:

bronzefighter wrote:

Bingo! I'm willing to be that this is the biggest contributor.

I would not use any water that RAISES PH by 1.4. Fluctuations are ok but worst I have ever seen normal water do is .3. I am not saying that it is not the case. Just saying a PH flucuation of 1.4 from water settling seems a bit extreme.

Oh...I totally misread that post   I though it was a drop. Well, I'm stumped!

mvrck wrote:  I replaced the normal carbon pad the build in filter came with with a Fluval ceramic bag,

Wouldn't it be messed up if you found out it was a bag of crushed coral instead of ceramics?!

Did you ever figure out what exactly was causing the PH spike?

I know with all the stuff going on in my tank I have all sorts of buffers to try to maintain a constant PH.

fishNAbowl wrote:

mvrck wrote:  I replaced the normal carbon pad the build in filter came with with a Fluval ceramic bag,

Wouldn't it be messed up if you found out it was a bag of crushed coral instead of ceramics?!

Did you ever figure out what exactly was causing the PH spike?

I know with all the stuff going on in my tank I have all sorts of buffers to try to maintain a constant PH.

I'm pretty sure it was the "lava rock" now. I'm also 99% sure the ceramics were just ceramics ([You must be registered and logged in to see this link.] is what I used), but I suppose they could have an effect as well. I had my family remove the rock, and do a 1/2 gallon water change. PH a couple hours later was down to ~7.4. So, going to keep doing small daily changes until it levels out. As for it possibly being the water needing to "air out", I don't think that it was likely, since we were using a container similar to this one:

[You must be registered and logged in to see this image.]

You have to puncture the top to allow air in else it won't empty properly, and it was tested almost 48 hours after first being opened. All signs are pointing to the lava rock being something else, in addition to probably a bit of a bump from the Onyx sand.

Thank you guys so much for your help and thoughts!

Well its prolly still lava rock, it just has some mineral deposits. Might leave it in a 5 gal bucket and change the water once a month or something to wash it away. Or use it on a tank where 7.4~ PH isnt an issue. Thats the problem with using any kind of rock, is rocks in nature are never 100% pure. Kinda lame for your case though.

This "oynx sand" as the product is called,, could be anything including crushed granite dust (Dark gray in color as Seattle_aquarists great discription) and some play sand in there too. It will raise the p.h. instantly. I deal with this P.H. madness every day as I'm on well water and use A.P.I. P.H. DOWN AND.or apple CIDER VINIGAR to drop back into to saner levels... The water has to buffer though to hold its level. I also use R.O. filtered (even for copper elements) store water at the refilling machines in Safeway stores that reads 6.8 p.h. and get 5 gallons worth for 41cents a gallon... can't beat it for nano's
Do a few different tests in clean fish buckets with different substraits and use the right p.h. test kits for high range, and lower range P.H. checks, rinse the vials with the actual water your testing as this will give you false readings too and use the lids instead of your finger to mix it.
Good luck and check back in soon. I will be setting up a small nano for my nephew so as well.