Measuring PO4

[brians_224]

Thanks again for your time.

What do you use to test for PO4? What do you recommend?

Now that I'm implementing your recommendations on refugium lighting - I'd like to watch my po4 levels for changes.

I've used a brand new salifert PO4 test kit. It reports 0. I've tested three different times. I had my water tested with a Hanna electronic PO4 test device. It measured .12 mg/l.

 

[Randy Holmes-Farley]

I use a kit from Hach (PO-19; www.hach.com ), but there are others that should be adequate. I'm surprised the two measurements that you took differed by so much. Was it the same water sample? Did the spectrophotometer sample sit around before testing?

 

[brians_224]

Thanks.

Not from the same sample, but from the same tank. The electronicly tested sample sat in a ziploc bag for about 45 minutes before testing. The salifert test was immediate.

I posted in the salifert forum - Habib was surprised as well.

 

[Randy Holmes-Farley]

You might try putting a tank sample in a bag for the same time period and testing it with the Salifert kit to remove that difference.

 

[brians_224]

I'll give that a try tonight. Do you think that there might be leaching from the plastic bag? Would you trust the results?

I've got hair algae - I need to get rid of it. I need to find something I can trust

 

[Randy Holmes-Farley]

It is possible. Someone in another thread noted leaching from plastic pipe when new. Bags may not have the same plasticizers, but may have other sorts of coatings.

You can treat the phosphate whether you can measure it or not. The algae still need it.