Is this how phosguard affects Ca and pH?

[krourke85]

Very excited to be using my new Hanna Phosphate checker with Phosguard to control my algae infestation.

 

I've noticed some of my other water parameters have gone askew. My phosphate was 0.31 and my calcium was 340ppm.

 

So I added a triple dose of Phosguard and enough Calcium to raise things to 420ppm (this is 20ml based on past experience). After 48 hours my pH had dropped to 8.0 and Calcium went up to 520.

 

I could throw out more numbers but essentially, my pH is staying low despite 2 doses of buffering.

 

My theory is that the phosphate binding to calcium (as calcium phosphate) is being removed by the phosguard, releasing ionic Ca into the water. The Ca is then binding with the carbonate becoming a precipitate and dropping the pH.

 

Does this sound right?

[seabass]

Are you also tracking alkalinity and magnesium? They are both key when dosing calcium and understanding pH swings.

 

Also, you want to lower phosphate slowly or it can affect your coral. Your target phosphate level should ultimately be between 0.01 and 0.03 ppm.

[GMay]

Your pH is not all that low. I think you need to worry more about alkalinity, as suggested by seabass. I would suspect that when you get your alkalinity to where you want it the pH will just fall into place at about 8.2. It is never a good idea to chase your pH with buffers as this tends to lead to other parameters going off track.

Good Luck!

[krourke85]

Its interesting that you mentioned Mg. I had recently superdosed Mg up to 2000ppm in my so far unsuccessful fight with hair algae, but recent test showed it was actually lower then normal at 1260.

 

My kH test ran out a while back, I've just got a new one now.

 

I thought buffer corrected kH and pH is a similar fashion, so I've been using the buffer to correct the pH and assuming it was correcting kH as well.

[seabass]

I thought buffer corrected kH and pH is a similar fashion, so I've been using the buffer to correct the pH and assuming it was correcting kH as well.

They are related, but you should correct alkalinity (not pH). Unless you are dosing something that affects pH or have a CO2 problem, it's normally not necessary to correct pH when alkalinity is within normal ranges.

 

PhosGuard does not directly alter alkalinity levels. However, you may notice an indirect connection between adding PhosGuard and KH. Phosphate itself acts as a buffer in water. Lowering the amount of phosphates in your tank will indirectly affect the alkalinity levels. Obviously, because PhosGuard works to remove phosphates, you may notice a slight drop in alkalinity initially.

source: http://www.seachem.com/support/forums/showthread.php?p=4051

[krourke85]

Thanks Seabass. Good Quote.

 

New tank parameters: pH is down to 7.9, kH is 7 and Ca is down 40 to 480ppm.

 

Also, I know phosguard says it is full after 4 days if your phosphate is above 0.02, but mine was 0.06 after 4 days and after leaving it in for another 3 weeks the same phosguard has dropped it to 0.00

So don't throw your phosguard out early!