Smaller Tank -> Lower PH?

[Johnson556]

Prior to my reefer 250 I had a 180G Tank (240G total system volume. Ph went from 8.05 at night to 8.25 during the day. The new reefer250 is essentially a 1/4 scale of my old system. Still running ESV, have an airline attached to the skimmer, mp40s/radions etc. The only difference is the 180G ran an ATS and the Reefer 250 runs a fuge with chaeto (fuge life is so much easier).

I'm noticing the PH will not fluctuate in the same range as before. The reefer seems to go from 7.9 at night to 8.1 during the day. I know its not a massive difference and still adequate for most, but I'm wondering why this is?

Pics for attention

 

[JustAnotherNanoTank]

Great looking tank!!!

I don’t know about size mattering, I have 20gal total and mine goes from 8.1 during the day and to 8.3 at night.