High Alk, Low/Unstable pH

[bryanh]

Hello Everyone,

I'm a bit new this hobbie and I find myself still confused over pH & Alk after reading various articles around the web.

Tank in question is a 46g reef w/ 6w per gal compact lighting. How do I get in a situation with high alkalinity and dropping pH (8.31-8.35 dropping to 8.18-8.20 w/n 24h tested using
calibrated digital meter w/ ORP of ~260, ~79 degrees F). The only
explanation I can come up with is high CO2 levels. While I have not tested CO2, I do have excellent surface agitation with 2 x magnum 350's and 2 x 600GPH power heads, seaclone skimmer modified via DYI instrunctions, approx 1.5 to 2" of space between water surface and aquarium lid, + air stone to get fresh air into tank surface. I also have a newer home which I have heard could cause elevated CO2 levels by the tight insulation/seal. I feel I have done all I can short of breaking the bank on such a small aquarium to keep gas levels close to normal.

I also use R/O D/I water w/ Reef Crystals brand mix, agitate for 24 hours
prior to use.

Questions:

1.) What other factors could cause high ALK, low pH

2.) I usually dose with seachem buffer to raise pH and reef builder alk
supplements if necessary. I have Kalk mix but decided to not use it yet w/ all of the human health hazard stickers on it. What would be a good
alternative to boost pH w/o raising Alk, I fear I could drop calcium levels
to far by over-using Alk+pH supplements.

3.) If over nitrification, over loading ( we have decently loaded system),
over feeding (we have cut back to once per day, small amounts of froz shrimp to figure out pH issue) were to blame for my pH dropping wouldn't this cause a drop in Alk also. ....or does Alkalinity only dissipate with time and even though it is a function of the stability of the pH adding enough acids to lower pH will not effect alkalinity?

Thank you for all your help!

 

[trido]

high alkalinity and dropping pH (8.31-8.35 dropping to 8.18-8.20 w/n 24h tested using
calibrated digital meter w/ ORP of ~260, ~79 degrees F).
Questions:

1.) What other factors could cause high ALK, low pH

I'm not sure if I understand your problem or explanation of things.
Are you saying that your PH is dropping form 8.3 down to 8.1? If so you have absolutily nothing to worry about. Im sure most would say that is ideal. Mine actually drops from 8.6 down to 8.0.
If I'm also reding correctly. Your Alkalinity is 260. Or a dKH of 7.4. Also within acceptable range.

 

[bryanh]

Yes, the pH is dropping from 8.35 to 8.15 w/n 24h. The problem is that my xenia stops pulsing below 8.3, above it, it pulses very frequently.

My ORP (oxygen redox potential) is at 260, my Alk well over >= 300ppm.

...of course my dosing methods with seachem buffer can't really raise above 8.3, sliding from 8.6ish down to no lower than 8.3 I think would be more ideal w/ sensitive animals.

 

[MartinE]

Are you dosing Calcium at all? If not then you could be lowering your Calcium with the dosing of Alk./Buffer supplements and that could cause the drop in PH. Alk./Buffer and Calcium are connected without dosing one or the other you get changes in PH and the one you are not dosing.
Oh and if your PH is dropping at nite when the lights go out that is normal, as photosynthesis is not going on and producing O2.

 

[bryanh]

Hi Eric,

Not dosing on the Ca very often maybe this is my problem, I think my best bet may just to use Kalk and be careful with it. As I understand it, Kalkwassar/calcium hydroxide will raise pH/Alk and available Calcium all-in-one, is this accurate?

I realize that a pH drop at night is normal w/o alternating sump lighting (don't have one on such a small tank). My pH test was done in evening after 3/4 of full-day sun at same time of day. I'm just trying to minimize the pH drop both over time and at night.

 

[MartinE]

Yes it will up your PH/Alk and you can overshoot with Kalk., so go easy on it if you try it until you know how much is enough to dose. If you are uncomfortable with the Kalk. dosing to start you could try a 2 part additive like B-Ionic, may be a little easier than the Kalk.

 

[EmilyB]

Get everything back in balance with some frequent water changes first.

 

[bryanh]

Thanks Eric, as I understand it most overshooting w/ Kalk is caused by extreme pH increases. If I add very slowly and test w/ digital pH meter, wouldn't this alleviate the concern of overdosing?

Can other overdosing occur w/ Kalk other than pH?

 

[MartinE]

Well yeah you can also run your Calcium up really high as well. IMO over 500 is to high so shoot for something lower than 500, but higher than say 300. You will probably be ok just test water perams until you know the right amt. Chemistry in a reef tank is a pain sometimes to keep in balance and like EmilyB said sometimes you have to do water changes, get back in balance and start over.

 

[bryanh]

Thanks Martin, currently my Ca tested in at about 330. As for water changes I do weekly 12-18%. At this rate salt dilution may be my only problem (r/o +kalk mix).

Speaking of water changes, I see many reef tanks have animals stacked all the way to the top of the tank. Is there any tried and true rules on length of time that certain animals can be out of water w/o causing harm during a water change? I understand that starfish should never be exposed to the air, are there other animals in this category? What about clams? In larger tanks I suppose you could simply change the sump water and not drop main tank, but that might not change much.

 

[MartinE]

You should not need to take any animals out of a tank to do a water change. If your crawlers are looking like they will be in the air when you do a water change just postpone it until they are lower in the tank. The other things that should not be exposed to the air other than starfish are clams, shrimp, scallops to name a few. I am sure there are some others that escape me that should not as well.

 

[bryanh]

thanks, probably anenomes as well?

 

[MartinE]

Yeah, see I couldent remember them all I knew it

 

[bryanh]

I took a sample of aquarium water, stirred it indoors for a few seconds w/ pH meter. The water indoors maintained a pH of 8.17. I took it outside for a few seconds, it immediately jumped to 8.31. Is this CO2 build-up significant enough to be a cause of concern?