pH questions

[jlinzmaier]

I use seachem buffer for pH adjustment and seachem builder an alkalinity raising agent. I have about 100gal total with sump, fuge, and display. I do 10 gal H2O changes every week and routinely add ca and trace elements in additions to iodine and multivitamins. Tank is moderately stocked with fish and lightly stocked with corals. Recommedations on buffer are to add 1 tsp per 20 gal twice weekly to less often if it's not needed. I've needed to add the buffer 3-4 times a week at the recomended dose to keep the pH at 8.3 otherwise it drops to 8.0 or below.

Alkalinity is between 4.0 and 5.0 meq The builder (alkalinity agent) is added MWF and sun at low doses to keep alkalinity stable
ammonia zero
nitrite zero
nitrate zero
phosphate zero
silicates zero
Calcium 420-450 Calcium is added nightly to keep at a steady level. I use reef complete because in addition to ca it also adds stronium and magnesium at common ratios to calcium.
I use RO water for my water changes. I have good circulation and excellent filtration.

If anybody has any suggestions about why my pH drops so quickly and how else I can keep it up I would appreciate it.
I also have frequent nuisance algae growth but I don't know if thats related at all.

 

[patpia]

Hi,

Are you using only RO for your water changes, I mean without and salt addition?

 

[Chris Jury1]

Most likely you've got excess CO2 dissolved in the tank water. This is actually a very common problem as buildings tend to have elevated CO2 compared to normal air. Also, respiration in the tank produces CO2 and can further elevate the pCO2 of the aquarium water.

Is this a reef tank? How are you measuring pH? Let's do a quick test to see if CO2 is the likely culprit. Take some tank water and measure pH immediately after removing it from the tank (measure away from the tank). Set up some tank water to aerate indoors and some to aerate outdoors and check the pH of each after an hour or two (make sure temp. of each is close to the same). If the pH of the outdoor-aerated water is significantly higher than the tank water then the problem is probably excess CO2. If the pH of the indoor-aerated water is significantly higher than the tank water, just aerating with indoor air will help. If the pH of the indoor-aerated water is not significantly higher than the tank water than the indoor air likely has an elevated pCO2 and may be the source of the problem.

cj