H2O2 cause drop in pH?

[burton2090]

Is there correlation between hydrogen peroxide and pH?  Or is it a secondary effect as the H2O2 kills algae?

 

Some background info.  I have a 165-gallon DT (200g total volume) that is 5 months old.   According to my Apex (see enclosed screen shot):

   -  lowest daily pH reading (8.06-8.11) occurs at 8am.  (just before the refugium light turns on and 2.5 hours before the display lights turn on).

   -  highest daily pH reading (8.35-8.39) occurs at 6pm (end of the photoperiod). 

 

Notice the pH drop this morning.  For the past two nights I have dosed 12mL of hydrogen peroxide.  This morning I noticed something interesting.  At 8am my pH was 8.27.  At 8:45 it dropped to 8.05.  I also dose 30mL Alk daily (5 mL every 3hrs) but the effect on pH is negligible.  10% WC on Sunday (explains the abnormal pH swing for March 1)    

 

Interested in your thoughts.

 

 

[Happyfeet]

I remember reading a study some time ago about the effects of H202 on Sea Water. Findings showed it lowered the pH slightly. I don't remember much about it.

[Crob5965]

I read somewhere that PH drops overnight when lights are out, that is why people run the Refugium light on an opposite schedule, not sure if i'm right or not, but this is what I have always done.

[madweazl]

I read somewhere that PH drops overnight when lights are out, that is why people run the Refugium light on an opposite schedule, not sure if i'm right or not, but this is what I have always done.

I do the same but I'm not sure how much of a difference it actually makes. I've never much concerned myself with the fluctuations as I dont have a controller and test it maybe four times a year. 

[zygote2k]

A question- why are you dosing h202 on a 5 month old tank?

[Happyfeet]

I read somewhere that PH drops overnight when lights are out, that is why people run the Refugium light on an opposite schedule, not sure if i'm right or not, but this is what I have always done.

 

Hey Crob, the diurnal cycle of photosynthesis and respiration is the cause of this rise and fall of pH. During the day organisms in the tank convert CO2 and H20 into carbohydrates and oxygen. The consumption of CO2 raises the pH while this process is taking place during the day. Likewise once the lights are out, the organisms still need energy, so they start breaking apart the carbohydrates in a process called respiration, releasing the CO2 back into the system and lowering the pH.

 

The larger the tank the smaller this swing will be, for example when I had my 75 gallon lightly stocked tank, the pH swing was less than .2, whereas oi my heavily stocked BioCube the pH would swing by 2 if I let it.

[burton2090]

Update: I dosed the usual 12mL last night after the lights went out and didn't observe any abnormal pH readings this morning.  So I'm not sure the H2O2 caused the drop...

 

A question- why are you dosing h202 on a 5 month old tank?

Rob, you're right.  I am dosing to clear the water column and combat some dense patches of GHA.  Yes I understand H2O2 is a band-aid and does not solve the root cause of the algae, which I attribute to a period of excessive overfeeding while I was away on a trip.  I have since corrected that.  Conventional wisdom demands a slow-and-steady approach during the first year to allow the tank to "find" itself.  Having said that, H2O2 (and the extra O2 it adds to the water) doesn't seem to affect anything in the system other than nuisance algae so I decided to experiment.

 

Thanks all for the input.   

[wangspeed]

If you're looking at 200gallons of actual water volume, 12ml will hardly do anything. I do that much on my 90 display + 29 sump. The only side effect I notice is zoas closing up, and my magician palys are rockin a super cool bleached look, maybe due to the peroxide.

[s2nhle]

Hey Crob, the diurnal cycle of photosynthesis and respiration is the cause of this rise and fall of pH. During the day organisms in the tank convert CO2 and H20 into carbohydrates and oxygen. The consumption of CO2 raises the pH while this process is taking place during the day. Likewise once the lights are out, the organisms still need energy, so they start breaking apart the carbohydrates in a process called respiration, releasing the CO2 back into the system and lowering the pH.

 

The larger the tank the smaller this swing will be, for example when I had my 75 gallon lightly stocked tank, the pH swing was less than .2, whereas oi my heavily stocked BioCube the pH would swing by 2 if I let it.

+1. How many corals do you have? have you see any grow? How many fish? how often you feed the fish? fish food contribute to the high nutrient and phosphate.

[burton2090]

If you're looking at 200gallons of actual water volume, 12ml will hardly do anything. I do that much on my 90 display + 29 sump. The only side effect I notice is zoas closing up, and my magician palys are rockin a super cool bleached look, maybe due to the peroxide.

 

You're right.  The (unofficial) recommended dose is 1mL/10 gallons.  I'll probably up the dosage a little bit.  And yes, I noticed one of my zoa colonies is less than thrilled.  Yet the other colonies are fine.

[Crob5965]

Hey Crob, the diurnal cycle of photosynthesis and respiration is the cause of this rise and fall of pH. During the day organisms in the tank convert CO2 and H20 into carbohydrates and oxygen. The consumption of CO2 raises the pH while this process is taking place during the day. Likewise once the lights are out, the organisms still need energy, so they start breaking apart the carbohydrates in a process called respiration, releasing the CO2 back into the system and lowering the pH.

 

The larger the tank the smaller this swing will be, for example when I had my 75 gallon lightly stocked tank, the pH swing was less than .2, whereas oi my heavily stocked BioCube the pH would swing by 2 if I let it.

 

 

Thanks for the insight, I remember reading this a couple of years ago when starting out, I have been doing the lighting cycle since day 1 just couldn't really remember why, I just knew I read somewhere that that was the best way to reduce PH swings, I have a 90gal with a 29gal sump and haven't ever really noticed that much of a PH swing, that being said after the 1st year I'm not really big on water tests ; ) things just seem to stay the same as long as I do regular  a WC