pH rising(sorry, kinda long)

[jiggerpolebill]

last weekend i set a 10g tank to use for fry. im using pea gravel from the home store, an AC150 filter and 50w Ebo-Jager heater. theres also an air pump/stone set up.

the way i started preparing the tank was, i took my filter media and placed it in an established tank for about two days. sat i used the water from a change from this tank to fill the 10g. i assembled this filter and hooked up everything and let it run til sunday.

sunday, i put in 2 molly fry as test subjects. they cane from another tank ofther than the one used to prep this one.

i tested the water today in the 10g to see how it was looking and found the following results:
amm - 0
nitrite - .5
pH - 8.2
the water from the original tank tested this way:
amm - 0
nitrite - 0
pH - 7.6
these are normal parameters for the original tank water

any ideas about the spike in pH? the 10g has nothing but gravel and rocks inside right now. the original tank has no live plants, just rocks and gravel and ornaments and plastic plants.

im guessing that one of the rocks is raising the pH. they all passed the vinegar test, but i feel like ive read somewhere that silica based rocks will alter pH. one other thing im wondering is: the original water comes from i tank i feel to be overstocked. im staying on top of maintenance on it because of this, but, how does water change when going from a heavy bio-load, to virtually none at all? could bacteria be dying and causing the change?

i performed a 2g water change on the 10g today and will retest tommorrow. thanks for info and advice.

[valerie]

have you measured your tap water after it has sit out for a while? sometimes the pH will rise when the CO2 out gases. I know mine goes up a bit from what it comes out of the tap as.

[OrionGirl]

I'm thinking the pH shift is more likely due to the cycling process.

Using the water from the other tank is actually counter productive, since the bacteria aren't free floating. All you're doing is importing wastes. 2 days isn't enough time for both types of bacteria to develop in the filter, so I'm guessing that there was a small bed of bacteria capable of processing the ammonia in the water, but no bacteria for processing the nitrites that resulted.

Silica won't alter pH. An extremely low pH will dissolve silica.

[jiggerpolebill]

oh yeah, one thing i didnt mention was i did add about half a cup or so of the substrate to the 10g as well. should i add a couple of more fry(molly - i currently have these out the wazzoo in another 10g tank) to assist? thanks for the info.

[famman]

Do yourself a BIG favor and put the fry back where they came from and continue with a fishless cycle.
If you innoculate (add gravel/substrate etc.) from an established tank everyday you will have very fast results.
I kick myself every time I think about the last time I did a cycle with fish.
good luck
:)

[jiggerpolebill]

as bad as this is going to sound, i didnt mind culling the weak by putting the fry i put in there, in there. ive got more molly fry than i can support really(even after the parents were separated) and the 2 out of the possible 60-70 i still have are still hanging in there, acting just like their siblings. i dont have any other fish to use them as feeders for and the LFS doesnt take for trade fish under an inch. i am going to keep adding gravel and doing water changes and monitor it til it gets through doing its cycle thing.