PO4 in RODI?

[r33fermaddness]

I’ve got a 90g tank about 4 months old now, I’ve been measuring high phosphate (.5-1ppm) in the tank since the start, I figured it was leftover organic die off from the dead live rock I’m using (which I did bleach cure and rinsed well before starting the tank) and that it would eventually taper off, which I also aided with a GFO reactor.
Fast forward 4 months, I’m still measuring 1ppm consistently, so I tested my RODI water I filter myself with an AquaticLife 4 stage system and collect in a standard Rubbermaid trash bin. The RODI water tested 2ppm, so I ordered and replaced the 4 filter canisters last night, flushed them, and filtered new water overnight. This morning, water is still testing 2ppm.

AquaticLife does sell a PO4 removal canister to go with this system, and I’m thinking that might be my next move, or I’m considering using something like Brightwell’s Phosphate-E to treat a full bin but that may become convoluted because I generally don’t go through the full bin before filtering more water into it.

Any thoughts/suggestions? Thanks in advance!

 

[xxkenny90xx]

Have you tested it in a different container other than your usual mixing container?

 

[r33fermaddness]

Have you tested it in a different container other than your usual mixing container?

I haven’t, just because I have the unit connected to a float switch that’s attached to the bin. I will tonight though, I’ll stick a clean cup under the drips and see what the tests say.

 

[r33fermaddness]

Update:
After testing the water in different containers, adding Brightwell’s Phosphate-E (which I discovered doesn’t work without mechanical filtration to remove the bound Phosphate, which my bin of RODI is not equipped with), purchasing and adding a Phosphate removal canister from AquaticLife (which I’m pretty sure is just GFO in their proprietary canister) and testing THAT water, and STILL getting a consistent 1ppm in the RODI water and tank water, I got a Red Sea Phosphate pro test kit. Hindsight; should’ve gotten the better test kit from the get go setting up the tank, much less before delving into Phosphate removal methods and equipment. Tested the tank water with the Red Sea kit and it’s reading .04!! Not gonna bother testing the RODI since I don’t think the tests are designed for freshwater in the first place, the only reason I was chasing that particular goose was the false PO4 measurement in the tank.
Moral of the story: If something is funky, verify your test accuracy - if that’s in question, get a more accurate test, BEFORE jumping into fixing a problem that might not be there

P.S. I should mention for archival purposes that the initial tests were done using API’s Freshwater/Marine PO4 test kit, which should’ve been another red flag from the start, but hey, lesson learned.