My pH is going up?

[Biotoper]

My tank is about 1.5 months old and the pH and KH have been stable at 7.7 and 4.5 dh for the last couple weeks, but today the pH is up at 8.2 and I was wondering if anyone had any ideas why.

dKH is still 4.5. Now my tap is pH 8.4 and dKH 2.2 - I've been doing ~5% water changes every 4 days or so. I initially added enough baking soda to get the tank to 4.5 and I was adding baking soda to the water change buckets along with amquel, but I haven't done so for that last few changes. I've got 2x2L DIY CO2 going - planning on having 4 soon - and they're bubbling, but I don't have any fancy diffusor. I just have the airline input at the base of the bioball compartment. I was going to see how much CO2 was getting dissolved from my 4 bottles before I set up a diffusor - I'll probably do a powerhead/gravel cleaner tube set-up, to add some more flow to the tank. NO3 was slowly dropping and has been stable at 2 ppm for the last week.

Also, I tested about 4 days since the last water change, before the next water change. My hope was that my pH would drop to about 7 with the DIY CO2, but the 2 bottles haven't had much of an effect, and now pH is going up?!

[anonapersona]

Do you have baking soda added to the yeast mix? Perhaps you have some traveling up the line into the tank.

Also, it may be that your water system has changed sources. I don't quite see how your tank is 7.7pH and the tap is 8.4 pH. You say you added baking soda to the tank to get the KH up. Does this mean that you began with RO or distilled water and now are adding harder tap water to the tank? -- confused --

[Biotoper]

I haven't used RO water or anything like that. My tap water (Boston, MA) is strange in that it is very soft and basic. The MWRA adds I believe calcium hydroxide to reduce lead leaching from pipes, which increases the pH while not affecting the hardness much (but my understanding of the chemistry of this is very basic). I think the tap water is low in CO2 and as it pumps through my tank it takes up some CO2 from the ambient air - not much, a couple ppm - which drops the pH somewhat. Adding the baking soda increased the KH but didn't seem to have any effect on pH.

There is a little baking soda in the yeast bottles, but probably only a couple drops at most have drawn into the tank.

[Biotoper]

I mullled it over, and I think the rising pH is due to my plants. I've been measuring the pH at night just before the lights go off. Since my DIY CO2 currently isn't raising the CO2 ppm much, I think after a full day of plant photosynthesis, all the CO2 has been sucked up, causing a rise in pH with no significant change in KH. So I think I need to just get my CO2 injections up to 10+ ppm. It maybe that 75 gal is too big for DIY but I'm determined.

[Kasakato]

Let a glass of tap water sit over night and then test it. Sometimes letting it sit can change the pH of the water.

[Biotoper]

My buckets of tap that I let sit a day or 2 with amquel test at pH 8.1

I tested my tank in the morning at it was pH 7.8, so it looks like I'm getting a 0.4 rise during the day and drop at night. At my dKH of 4.5, this translates to a change of only ~1ppm CO2. I really need to get my DIY CO2 system working properly. :(

[Swimfins]

I have diy co2, 5 x 2 litre bottles on a gang valve, going into the intake of the filter on my 66g. At first my ph was 7.2, kh 3.6 (only 8 ppm co2) Finally it held steady at 7.0, kh3.4 yesterday afternoon (dosing 10ppm co2) This morning ph is 6.8, kh is 3.4 (dosing about 16ppm co2)

My ph will probably rise a bit after lights out. Stabilizing co2 on a big tank can take awhile. Its taken me about 2 weeks to get to this point. I started with 2 bottles and added one at a time. I am at 5 bottles now. The bottles have lasted about 9 to 10 days each. The ph of my tap water is 7.8

[TONO]

I have two large bottles hooked up to my co2 diy on an 80 gallon tank. Going into an aquaclear with tons of filter s floss by the output to help absorb the co2. I get about 10 to 14 ppm of co2 depending on the temperature of the room. So It can be done but it just takes alot of tweaking. but my mixes dont last very long a week at most.