Constant ph drop????

I have a 75g reef tank with 170 lbs of live rock, 90 lbs of live sand, 20 lbs of crushed coral in a eshopps 100 sump. I run a algae scrubber with a 10x10 screen for filtration an a coral life 36 watts uv sterilizer an do a 10% water chane a week. I keep having a ph drop, it stays around 7.80 to 7.90. I use kent marine ph super buffer to raise ph but it doesn't stay will drop by the next morning. The water the I use out of my RO/DI is low about 5.60. Should I add the buffer to the auto top off water or get a doser.

 

What's alkalinity at? You've probably got low alk.

 

how does everything look in your tank? keep in mind the temp of the water can make the Ph change

Mine runs about 8.03 during the day and 7.92 at night. but its stable

 

Could be low Oxygen as too much Carbon Dioxide will lower pH. Try an air-stone (or two) and see if that helps.

 

What salt are you using?

And when you say always dropping, do you mean it is higher and then always drops to 7.9 ish or it is stable at 7.9?

 

When I add 3 tsps of the ph super buffer it goes up to 8.1 but the next day it is back down to 7.8 to 7.9. I'm using Tropic Marin Pro

 

Are you testing it at approximately the same time of day or night every time you test?

Can you increase the surface agitation.

And yes I agree alk and magnesium level would be more informative. Also if your swing is from 7.9-8.1 I would not be too concerned at all.

Depending what your other water chemistry values come out at like ca/alk/mg you may want to try a slow kalkawsser drip.

 

+1. Surface agitation is an easy fix.

 

Can you increase the surface agitation.

Not really sure what you mean by this.....

But yes it test the ph before I add the buffer then after and throughout the day. I tested the KH an it was 9 calcium was 430ppm I don't have a Alk or mag test I'll have to go get them.

 

Do you have lots of ripples on the water surface in your tank? The more ripples you have, the better your gas exchange (CO2/O2) will be. If the your water surface is very smoth, you may want to point your PH's up to create ripples.

KH is an alkalinity test, so you're good there. Mg is a separate test.