What happened to my pH?

[Elle2]

I am in day 13 of my cycle and everything seems to be going smoothly except my pH which has dropped below 6. I have been able to find information on why pH levels increase but not on why they decrease.

I am assuming that its not my tap water because my first test (4 days into cycle) showed a pH of 7. I have not done any water changes or added any materials since then so I have no idea why mine would drop so drastically or what to do about it.

Any thoughts or suggestions? (tank details below)

20 G
two Java ferns (one corkscrew grass that died and was in tank languishing for a few days)
pool filter sand
two pieces of driftwood

[Jchillin]

two pieces of driftwood

Driftwood can soften water but nowhere near an entire point. I agree it isn't your tap water. What are you using for an ammonia source and what type of test are you using?

[Lonewolfblue]

At this point, I would do a 50% PWC to bump the ph up some, then see where your ph and ammonia are. The decomposing shrimp should still be maintaining a constant supply of ammonia, so you won't stall the cycle by doing the PWC's. And since it's fishless, you could try adding just a little fresh baking soda to bump up the kh a little, which will also help the ph be a little more stable. As for how much, maybe someone can chime in. I just used PWC's myself in the fishless cycle to up my ph.

[newfound77951]

Do you know what your kH and gH are? If they're very low then your pH will be susceptible to sudden changes.

[Elle2]

The most recent data I can find indicates that the pH is quite low- 6.2-7 so I am now wondering if there was something in my tank that raised the levels during the first week. The kH seems to range from 3.8-4.6 but I couldn't find any data on the gH.

I will test the pH on some tap water- to do this do I have to let it sit for a while or do I test right away?

If my water is naturally low and I can't add baking soda once I have fish does anyone know what I can do to raise the pH?

[rich311k]

You can put some crushed coral in your filter it will raise your PH and keep it stable. You only have to replace it every 4 months or so. I would wait until your cycle finishes.

[Jchillin]

I will test the pH on some tap water- to do this do I have to let it sit for a while or do I test right away?

Let it sit out overnight prior to testing. You haven't mentioned what type of Ph test you are using.

[Elle2]

Its a freshwater master test kit.

[Lonewolfblue]

Once the cycle is complete, the ph will stabalize. Nothing to fear there. It's just during some cycles, the ph tends to crash. But that's quite normal for some people. A quick PWC will help keep the cycle from stalling. How's your ammonia and nitrite looking?

[maxwell1295]

If your tap water is very soft to begin with, adding driftwood can (and will) cause a pH crash. It happened to me. I use baking soda to up the KH (and pH) and add some with every PWC. I try to keep my KH up around 6-7 since I am now injecting CO2. Ph is around 7.0. Prior to do this, my pH was 6.6 and KH was 1dKH.

Edited: I meant KH and not GH