GFO & PH

[pinhigh1886]

So you may have read in another Thread that I overdosed my tank with Calcium with my Apex Controller acidentily a few days ago. You can see that on the attached graph. What you will also now see on the graph is my PH dropping like a rock yesterday into today. My Apex was sending me alarm texts all night every hour telling me that my PH was below 7.9. I am trying to figure out why. I changed Activated Carbon (which I believe if anything would raise PH) and changed GFO (which I am now reading can drop PH rapidly after initial use or replacement). Has anyone else seen a drop in PH right after introducing GFO or replacing GFO? FYI I also turned off the Cal doser for the last two days due to the OD. Cal is well over 500 so I am slowly trying to bring it down by not dosing cal and small water changes. I have done 4 gallons so far and my system is about 110 gallons.

[binford4000]

IMHO four gallons will not change your calcium level. You might want to consider doing atleast ten percent then test in a few days. I have never seen that much of a drop in Ph from GFO either. How much GFO are you running. I am assuming that it would take a large amount to effect the buffering capability of your water column. It is important to note that your water will become acidic once it comes close to 7.o. 7.9 is a little low but not horrible. What is your alk at ? Alk and Ph work together but to much is also not a good thing too. Good luck

[pinhigh1886]

I am doing a 2 - 3 gallon water change each night this week. I would never do 10 all at once. I used to but I think it had ill effect on my tank. I have probably done 8 gallons now and the Cal is coming down but still over 500. My Alk is dead at 8 and has been since I got my dosers. I agree that GFO shouldn't make that noticeable of a difference but not sure what else it could be. It recovered nicely yesterday and only dropped to 7.95 last night. I am hoping to get my PH up a little when I get the Vortech MP40 going tonight. It should add oxygenation and raise PH slightly. If not I will dose a little higher Alk and try to maintain 8.1-8.2 PH with a smaller dip at night. OH I added a large Rainbow Wellso, Squamosa Clam, and a small Litho frag this weekend as well? Not sure if that did anything. I will monitor the graph next time I change Carbon and GFO and see if I get the same drop.

[redemer123]

your system is 110 gallons and you wont do a 10g water change all at once? Even if you did a 10 gallon change at once, it will hardly do anything to your system. Also, here's a nice little write up on ferric oxide and its affects on oxygen absorption. Heterogeneous Oxidation of Fe(II) on Ferric Oxide at Neutral pH and a Low Partial Pressure of O2? - Environmental Science & Technology (ACS Publications) If you don't understand it i'll be happy to put it in non chemistry terms.

[pinhigh1886]

Yeah it is a 90 Gallon DT with 20 Gallons in a 30 Gallon Sump and no I will not do a 10 Gallon water cahnge at once. I did all the time when I had FOWLR but with $1000's in SPS and other creatures I am not taking (2) 5 gallon buckets of water out of my tank and then adding new all at once. I heat my make up saltwater and let it age for 2 days and still wouldn't. I just don't like pouring pure new water at slightly different temp and salinity all over the top of my corals at heavy flow. Plus it's much easier to do with a 1 gallon pitcher VS a 5 gallon bucket. JMO and practice. I am not at all saying you can't. Now if I had some major problem which warrented a major water change I would do it in a second to save my tank. Just not as a standard practice.

I read the article but don't see where they show relationship to PH increase or decrease when GFO introduced. I only see that the study was done at neutral PH? Can you dumb it down for me and give me the conclusion they came up with? Thanks for researching

[redemer123]

The article doesn't explicitly say ferric oxide will reduce pH or raise pH.However, It does say that Ferric oxide has a relationship with oxygen in terms of sorbtion. Which basically was the answer I was looking for, this means that oxygen essentially becomes attached to the substance. Since the GFO is ferric oxide just in granule form, I think I am reasonable to suggest that the GFO may deplete a small amount of oxygen from your tank and lower your pH a small amount. You never actually said how much GFO you are using at once, are you following the directions or just using to much? could be why your seeing pH changes.

[pinhigh1886]

I am using the small Phosban Reactor and filling it maybe halfway. Not too much I don't think. I did not have my Apex last time it was changed so I was not graphing PH. I will watch it next time and see if I get the same dip. It really didn't dip too far 7.9 but I was just interested in the reason. I am hovering around 8.0 so my daily swings go from 8.1 - 7.9. I am adding a MP40 tonight which should help oxygenate my system which could raise PH. If not I will up my alk dose to put me more in the 8.2 - 8.0 range daily.

[redemer123]

If you started out with all that at once that is likely the reason for some minor instabilities. A wise man once told me; "In a reef tank no rapid change is good, even a change for the better." start with small amounts of GFO and progress to more, it may shock the system to start with a lot. If you are referring to the phosban 150 being half full that's actually quite a bit. I wasn't even a quarter full on my 180g system after long term use.

[pinhigh1886]

No I have been running GFO for a year now. I was just changing it. It is a little under half full.

[pinhigh1886]

I use a refractometer so it is always almost exact. Again I just prefer smaller water changes. Most of all because it is easier than lugging buckets around like I used to but also because I think it's better. Again, it is just my process! I don't think my tank would change much even if I did a 20 gallon change. My next big purchase is going to be a Auto Water Change System. I will then do a (1.5 gallon) change daily for this tank which would be close to 10% weekly.