why does my ph drop

[mmd]

ph in the tank under 6.0 (test limit)
150 gallon tank, right after 30% water change ph in the tank under 6.0 (test limit)
ph of the tap water is 7.6
i have some driftwood but cant imagine this is lowering it that quick
72576

[mmd]

well thats my tank upside down (right sude up for australian viewers, lol)

[mmd]

i have a 150 gallon tank, 18 by 6 foot, temp 84 degrees, no2 undetectable, no3 between .5 and 10.
9 discus between 4-6 inches,10 small cory's. one large piece of driftwood, well aged pool sand substarte.
2 pair discus spawn regularly.
filtration: fluval 304 with carbon and plenty of ceramic rings and a fx5 with ceramic rings.

[lipadj46]

your water is soft mine does the same thing. If you age it 24hrs does the pH drop.

[cjr8420]

off gasing changes it. sounds like u should age ur water

[roundfishross]

toss some crushed coral in the filter and it should solve this problem

[TNT77]

off gasing changes it. sounds like u should age ur water
+1

[jimg]

what is your kh?
off gassing would make the ph rise,(in most case). nitrification or adding acids would make it go down.
If your kh is on the low end, I agree with crushed coral. more wc's may also help. you will have to experiment with both to see which at what amount stays stable the longest.

[mmorris]

You can buy a kit that measures kh. You want a reading of at least 5 with the test drops. I add sodium bicarbonate (baking soda) to up the kh on my water.

[mmd]

my kh if i did it right is 1.6

[mmd]

so i added less than 2 oz of baking soda and the kh shot up to 10

[Alight]

What was your pH, then? I suspect you might have gotten back on the scale, but no for sure. 30% water change with 7.6 water is not enough to counter act your acid level. Your water will get acid because of the nitrogen cycle because acid is one of the other by-products of the nitrogen cycle. Once you "break" the buffer or your water, it will get quite acid quickly, and be difficult to bring back up. So, you can either do a much more massive water change (70% or more), or add small amounts of baking soda, a bit at a time, and bring your pH and kH back up. I'd suggest the baking soda on a regular basis if the rest of your parameters (probably only the nitrate to worry about at this point) are really in a good range. Nitrate test kits are notoriously inaccurate, so I'd try a different test kit to confirm your water is OK before you go with the routine bicarb adjustment.