ph dropping....why?

[McLean]

Hi guys! My 25 gallon tank is approximately 3 months old. For the first couple months the ph was a steady 7.4. in the past few weeks the ph is testing around 6.4. and i dont know why. It is a moderately planted tank with moderate lighting (25 gallon/ 65 watts) and no co2. I have lost a couple fish due to ich and had to increase the tank temp but replaced the fish soon after and tried to keep everything relatively stable. I've never had ammonia or nitrites and nitrates have never exceeded 20ppm. Can someone please explain if a decrease in ph normal at this stage, why my ph has changed, or if i should be concerned...? I did leave town for a few days so the lights were off but i made sure they got extra sunlight during that time. The ph has remained low since then even though i am now back on the regular lighting schedule.

Thanks!
Rochelle

 

[jcolon]

pH could drop for a few reasons, but four that sounds likely for your scenario

1. Have you been using test strips to check your pH? If so strips are notoriously inaccurate. Many AA member recommend the API test master kit.

2. Your PWC source has changed. If you have been using tap, maybe your municipality made a change like filtering out some of the hard minerals?
The best thing to do is test your tap after letting it sit out for 24hrs.
Or have you changed to a different PWC source, RO/DI?

The first two I would think is capable of lowering your pH by one, the next two I'm not sure about.

3. You introduce Driftwood , Peat ... the tannins would lower your pH

4. The plants were not getting enough light for photosynthesis so they also use O2 and give off CO2.

 

[McLean]

Test strips...ugh... I learned the hard way that they are crap. I use API.
You are right, I should test my tap water. Doh! I shouldve done that before posting but it didnt occur to me that the city would just up and change the water all of a sudden. Other than that I was leaning towards the light issue with my plants. Ive heard that co2 issues can cause ph crashes but i'm not very knowledgeable about how or why that happens. I'll know more about the city water in about 24 hrs if anyone has anything to add in the meantime, I'm all ears.