Grrr, I hate pH swings!

[BSJF]

The 40g breeder is 7.8 at night and 8.49 by late afternoon. The pH probe isn't temp calibrated, so these are off a bit (anyway I don't think it is). The tank is around 80 degrees.

I don't drip kalk and really don't want to have to.

I do keep macro in the tank, don't have a sump or skimmer and really don't want to get one either. I skim manually from the top with each water change.

I added LEDs recently, would they cause this?

I also added chem-pure a few weeks ago, which if anything is supposed to stabilize it.

I'll have to test everything today. Last week it was 120 ppm alk and 400 ppm calc, I did a small water change with 160 ppm alk and 440 calc, so I would imagine it is somewhere inbetween those values. Will post when I am done testing.

Any suggestions?

[Europhyllia]

The macro algae will take in CO2 and release 02 during the day. But during the nighttime, they will respire, meaning they take in O2 and release CO2. The CO2 produces carbonic acid which will lower the pH.

So you don't want to drip anything at night and you don't want to have a sump ... the only two things I could think of would be: get rid of the macro or get one of those hang on fuge things to run at night

[BSJF]

So your seahorse tank has macro in it. Do you get pH swings? Or are you running kalk at night?

Here are my test results. I will add a bit of mag, but doubt that would be the prob.
425 ppm calc
150 ppm alk
1200 ppm mag
80 degrees

[Europhyllia]

Mine aren't as pronounced as yours. I run a fuge with lighting at night

[BSJF]

The strange thing is I had macro in the baby tank all the time, much more than I currently have without any swing. I wonder if I left on a 1 w white LED at night over the corner where the macro is if that would help.

[allan]

... or, could you put an air pump and an inline oxygen filter thing into your overflow? This would provide additional oxygen at night. Not sure if it would be enough to combat your swing, but it seems low budget.

[hobogato]

maybe the air in your house is more stagnant now? if you have had the windows closed up and used the heater, you may have a buildup of co2 in the air inside your house causing the pH to change more?

The strange thing is I had macro in the baby tank all the time, much more than I currently have without any swing. I wonder if I left on a 1 w white LED at night over the corner where the macro is if that would help.