I cannot bring my Phos level down, always above 1.5

[CyberGuy]

I have a 20 gallon mixed tank with about 50% SPS. It only has a H.O.B refugium without any mechanical filter and no skimmer. I use reverse cycle light for my refugium.
I just tried putting a small bag of Rowasphos in my H.O.B refugium but since it does not tumble, the Rowasphos is not doing much.
I do weekly 20% water change and use RODI water with 0 tds.
I only feed small portion every other day with frozen mysis. I only have a small clown, a small yellow coris, and a small bangai.
My corals/sps are doing o.k but not growing much with only decent coloration. Zoas are doing great though.
I use Hanna Phos checker. The solution always turn light blue color after the powder is put in and dissolved, thus showing a high 1.5-2.0 level. I just test my friend's great sps tank water and it is 0.0. Too low, I kniw, but I just want to make sure my kit is working right. His tank is doing great though.

Please advice on a way to bring my phos down. Thank you.

 

[motortrendz]

At that level it will take a long time to come down as I'm sure is absorbed into your rocks and will slowly lack back out as you remove it. I would have said use lantanum chloride but you dont have a skimmer to drip it into.

 

[doodledreads]

I had the same issue, until I learned about Lanthanum Chloride. It brings down phosphates rapidly, and from there, you can use other methods like GFO or Aluminium Oxide to keep it low. The thing about the phosphates is it binds with substrate and rock and thats why water changes do not help. I use PhosphateRx but there are others. Just be careful you don't overdose it as it can strip phosphates completely and thus can harm your corals.

 

[doodledreads]

At that level it will take a long time to come down as I'm sure is absorbed into your rocks and will slowly lack back out as you remove it. I would have said use lantanum chloride but you dont have a skimmer to drip it into.

You don't really need a skimmer, a 5 or 10 micron filter sock or tightly packed filter floss can also remove the precipitate.

 

[motortrendz]

You don't really need a skimmer, a 5 or 10 micron filter sock or tightly packed filter floss can also remove the precipitate.

That's true. Forgot about that. In the past when I used it I just dosed in through the top of the skimmer into the bubbles sonit would bind and be removed.