Inconsistent Phosphates
 

I've been battling high phosphates ever since starting the current tank (18 months ago). I bought the whole setup from another reefer, who (I believe) neglected it for months. Not knowing any better, I used everything: his rock, his sand, etc. When I first started it, in Nov 2012, the phosphates were over 1 ppm. Over time I brought them down to below 0.1 ppm, by keeping to a rigorous water changing schedule and running ROWAphos.

What irritates me is the swings in phosphate levels that I noticed over time. Below is a table showing the results over the past couple of months. I test using a Hanna Colorimeter.
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DATE Phosphate Levels
13-Mar-14 0.15

15-Mar-14 0.17

16-Mar-14 0.11

18-Mar-14 0.1

21-Mar-14 0.08

25-Mar-14 0.12

27-Mar-14 0.13

30-Mar-14 0.13 Changed ROWAphos 2-Apr-14 0.31

3-Apr-14 0.08

6-Apr-14 0.04

10-Apr-14 0.06

15-Apr-14 0.09 Changed ROWAphos 17-Apr-14 0.3

20-Apr-14 0.1

22-Apr-14 0.3

24-Apr-14 0.1

29-Apr-14 0.06

30-Apr-14 0.05 After Shanging ROWAphos 4-May-14 0.06

7-May-14 0.48


I am totally puzzled. Any ideas/suggestions?

I forgot to mention I've had a refugium full of macroalgae and a turf algae scrubber for months. I also started running biopellets on April 1 and have been dosing kalk automatically since January. I don't have a high bioload (6 2-3 inch fish in a 55 gal with a 33 in-line refugium).

Phosphate test kit inconsistent maybe ?

Sounds like possibly the LR you got with the setup is packed and leaching - Old Tank Syndrome

You may want to consider buying some replacement LR, cure/cook it in a tub until it's clean, and then swap it all
Then you can cure the old LR and sell it

A Guide - Live rock; Curing & Cooking, and Tank Cycling

Might want to change out the sand too , could be full of crud . I reused my sand and my skimmers been pulling nasty gunk for 5 months now with no bioload.

+1
I missed that part

extremes can probably throw out as a botched test, then device is only good for +- 0.04ppm

Thanks, I considered it, but I have all kinds of coral encrusted on the rock and wouldn't want to lose it.

I'm about to do an upgrade, and I will be replacing the sand.

Still, has anybody encountered this level of inconsistency? From 0.05 to 0.5 within a couple of weeks? And then back to below 0.1 ppm?

I know people on here that love the phosphate hanna checker but Ive always had varying results when using it. May not be whats going on here but it annoyed me to the point where i dont use it anymore. Im also battling a phosphate issue and started losing some of my sps after I hooked up a GFO Reactor. Frustrating as hell.