Phosphate and algae

[Reef.]

When a tank is inundated with algae but your po4 reading is zero or low, that is an accurate reading is what I believe or is it true as I keep reading that in that scenario your po4 is actually high, the po4 test giving a false result because of the algae?

My thinking because the po4 has now been used up by the living algae it is no longer available for other processes to use, therefore trying to reduce po4 with rowa would be a mistake?

 

[Randy Holmes-Farley Verified Community Expert]

When a tank is inundated with algae but your po4 reading is zero or low, that is an accurate reading is what I believe or is it true as I keep reading that in that scenario your po4 is actually high, the po4 test giving a false result because of the algae?

My thinking because the po4 has now been used up by the living algae it is no longer available for other processes to use, therefore trying to reduce po4 with rowa would be a mistake?

Yes. My suggestion is to target at least 0.05 ppm of measurable phosphate. It is certainly true that no matter why it is low, corals only see what is in the water and low value may be depriving them of what they need.

 

[rishma]

When a tank is inundated with algae but your po4 reading is zero or low, that is an accurate reading is what I believe or is it true as I keep reading that in that scenario your po4 is actually high, the po4 test giving a false result because of the algae?

My thinking because the po4 has now been used up by the living algae it is no longer available for other processes to use, therefore trying to reduce po4 with rowa would be a mistake?

Good question, relevant to an ongoing debate (which In think I’m losing :)

The test result is not likely false, I agree with the second statement that the PO4 is likely being used up by the algae.

I do think the use of phosphate removing media could be part of the solution but you have to be very careful, especially if you have corals. It’s not an ideal application of rowa or GFO. If the measured phosphate in the water is low and you strip it to zero, you may have problems.

I would manually clean out as much algae as possible and then see if phosphate begins to rise. If so, you could use a small amount phosphate remover to sequester additional phosphate being added to the tank.

My friends will tell you forget about phosphate level and add herbivores instead. In this case, I’d have to agree with them.

 

[Waters]

Anytime you test for phosphates it is a snapshot at that point in time. As stated, regardless of the reason you are showing 0, other inverts that require phosphates are starving.