help me understand phosphates

larryhaynes · Nov 23, 2015

hello all, i am currently running bp and gfo in reactors , my po4 and no3 are ZERO..
i know this is not a good thing but is it REALLY a bad thing in an sps tank? i mean i had a 40g mixed reef before this NEW tank and was always fighting nutrients. so i decided to start off on the right foot with the new setup and am having problems getting po4 and no3 up a little i know it may sound stupid but i dont want to have the problems i had before!!! how do i safley get them up without turning off the reactors ? or is 0/0 ok what are the cons if i let it be ? 76g dt 30g sump 5-6 fish!!!

Randy Holmes-Farley · Nov 23, 2015

How are you measuring? Different kits have different capabilities for measuring low levels. In other words, not all zeros are the same.

samba_dad · Nov 23, 2015

I had a similar issue with my setup using Red Sea test kits. I fed the fish a little more and put the protein skimmer on a timer for 4 hrs a day. That seemed to do the trick and I have 1-2 ppm NO3 and a measurable amount of PO4.

larryhaynes · Nov 23, 2015

Ok sounds like a plan my skimmer goes on timer!! Let's see what happens

larryhaynes · Nov 23, 2015

I use Hanna for po4 and salifert for no3

Randy Holmes-Farley · Nov 23, 2015

larryhaynes said:
I use Hanna for po4 and salifert for no3

Which Hanna? A 0 ppb on the HI736 is low enough that it is worth considering allowing it to rise. A 0 ppm on the HI713 may not be too low.

larryhaynes · Nov 23, 2015

I have 713 but haven't used it in a while I've been using 736

Randy Holmes-Farley · Nov 23, 2015

OK, then it's reasonable to back off on the export or add more fish foods.

larryhaynes · Nov 23, 2015

Do you think skimming too much

larryhaynes · Nov 23, 2015

How should I go about backing off should I turn off media reactors or should I turn off skimmer

larryhaynes · Nov 23, 2015

So the 713 and the 736 are different? The 713 is the larger of the two I would assume it's more accurate maybe I'm wrong? Which one should I be using consistently I tested phosphates earlier today with the 713 and they read 0.02 when I use the smaller one 736, it says 0.00

larryhaynes · Nov 23, 2015

Are the reagents different for the two I spoke to Hanna. A while back about the alkalinity reagents because they accidentally sent me once for freshwater and they said it didn't matter they were the same

GreatWhiteTang · Nov 24, 2015

I would not turn off the bp reactor ... The pellets won't tumble and the bacteria will grow them together in a sense .. Gfo reactor should be a low tumble usually with a smaller pump anyways .. Just give your fish some extra food for a while

apex003 · Nov 24, 2015

Randy - what value / range would you consider reasonable using the HI736?

larryhaynes · Nov 24, 2015

I'm listening guys thanks for all of your help

Randy Holmes-Farley · Nov 24, 2015

larryhaynes said:
Do you think skimming too much

High skimming alone does not usually end in phosphate too low, but the GFO can. I'd personally back off on the GFO.

Randy Holmes-Farley · Nov 24, 2015

larryhaynes said:
So the 713 and the 736 are different? The 713 is the larger of the two I would assume it's more accurate maybe I'm wrong? Which one should I be using consistently I tested phosphates earlier today with the 713 and they read 0.02 when I use the smaller one 736, it says 0.00

They are different in that the 736 is a bit more sensitive. Which is more accurate in your hands is hard to say, but the 736 has a claimed uncertainty (by Hanna) of about +/- 0.015 ppm while the 713 is +/- 0.04 ppm phosphate.

I typically recommend 0.02 ppm as a good target, but 0.01 ppm is not generally too low, especially if you use coral foods too.

apex003 · Nov 24, 2015

Just to make sure I understand the phosporous to phosphate conversion for the 736:

0.02 ppm phosphate is approx. 7 ppb phosphorous, correct?

(7ppb P x 3.066)/1000 is ~o.02pppm PO4