View Full Version : pH, alk. Water changes, or start dosing?

09/21/2010, 08:10 AM
Here's a little background to help evaluate the problem.

My system: !50 gal tank, 20 gal refugium, 30 gal sump. Tank has about 120 lbs live rock, 4 Koralia 750', and a return pump of about 1100 gph, and a 2" aragonite sand bed. Refugium has caulerpa and a 3" aragonite sand bed. Sump is Marineland model 4, with two towers of mechanical filters and carbon pads, and 2 large biowheels. Marineland 300 gal skimmer. NextReef reactor with GFO tumbling nicely.

System has been running for 10 weeks, with a few softies, shrooms, and 1 acro. No big demand for Calcium, I assume. Started adding the fish from my 110 that was/is QT. Fish as in what's in my sig. pH is down to 8.0, alk is down to 2 at the end of the light period. Calcium is 440, ammonia, trites, trates are 0, SG is 1.026, temp is 78-82

I don't expect a big demand for calcium, yet. I think the pH and alk are simply being consumed by the processing of the added fish bioload, right?

Can I get the pH and alk corrected with larger/more frequent water changes? Or do I have to start dosing as a better way? Or something else?


09/21/2010, 08:33 AM
If you have coralline algae growing on your rock, they will consume a significant amount of alk and calcium. So you will need to add alk and calcium to maintain proper levels to keep the coralline happy.

09/21/2010, 11:31 AM
The alk you stated is 2, is that ppm or meq/L? What is the magnesium level?

09/21/2010, 01:09 PM
It's meq/L. It usually runs about 4, and ph usually at 8.4, until I started adding the fish. Don't have a Mag test, yet. It's on my wish list.

So, Cliff, are you saying I will need to look into dosing as a general rule?

BTW, thanks for the replies!

09/21/2010, 01:56 PM
Your welcome. ;)

If your alk level is dropping below the recommended 7-11 dKH then you will need to supplement alk. For maintaining your alk or increasing it you can use pure baking soda with no addtives. The chem calculator will tell you how much you need to add for your size system.

If your calcium level remains fine, then you will not need to dose for it until it drops below acceptable levels between 380-450 ppm. Many salt mixes are high in calcium now.

Many salt mixes are high in mag as well now. Mag is used slowly, so if your salt mix is high in mag, you may not need to supplement it for a while until it drops below the recommend levels of 1280-1350 ppm.

Reef chemicals calculator

09/21/2010, 02:17 PM
So all you did was add fish and your Alk and pH started to become depressed? How about recent water changes or changes in salt vendors?

09/21/2010, 03:45 PM
So all you did was add fish and your Alk and pH started to become depressed? How about recent water changes or changes in salt vendors?

Pretty much. I had a tank running with the coral and inverts only, feeding sparingly, doing 10% water changes weekly with NeoMarine reef salt by Brightwell Aquatics. Everything was stable. I added fish, and was more concerned about ammonia and trates, so I was checking that daily. No spikes, no levels at all. Checked the pH last night, 1 week later after I added the fish, surprised it had come down. Checked alk, and that was down too. 10% water change was just done with RODI water, aerated/mixed with powerhead overnight just last Saturday.

09/21/2010, 09:01 PM
If the pH is dropping, that might indicate a problem with aeration, although 8.0 is high enough that I wouldn't worry much yet. The increase in the consumption of alkalinity and calcium might be due to the nutrients the fish are adding to the water column. :) All in all, everything sounds fine, although I'd make sure the water surface was getting a lot of agitation, to prevent films from building up.