I replaced the lid on my DT. Is a pH change of 0.4 overall safe?

[kdx7214]

The other day I made a mesh top with a window screen repair kit to replace the existing solid glass top on my 75g DT. After I did this the pH jumped from around 7.9 to 8.3 (with lights on). Is that safe and/or normal?

 

[piranhaman00]

If by jump you mean over the period of 12 hours or so then yes and yes.

 

[Formulator]

The other day I made a mesh top with a window screen repair kit to replace the existing solid glass top on my 75g DT. After I did this the pH jumped from around 7.9 to 8.3 (with lights on). Is that safe and/or normal?

Yes, it is OK. My tank used to cycle almost 0.5 pH units on a daily basis before I started my refugium on opposing light schedule. Your tank is getting more gas exchange now, which is a good thing in general. Your corals and any algae consume CO2 during daylight, increasing pH. They release CO2 at night through respiration, lowering the pH (they are actually always respirating, but not important for this discussion). With your top now open to more air exchange your water releases more CO2 and equilibrates better with the surrounding air composition which will raise your pH as you observed. Your tank will also benefit from increased oxygenation, which is great for your fish activity levels and general health of all the inhabitants. I’m really not sure why anyone keeps glass lids on aquariums TBH.

In addition to the pH effects, you will need a lot more top off water now, and your heaters may get more use due to evaporation and its cooling effect.

My tank pH for example: