Coral qt phosphates @ .33 - how can I lower them?

Biff0rz · Jan 1, 2021

I have a coral qt and did a test today. Nitrates were at 15ish and po4 was at .33. So I did a water change, fairly large, 50%. Nitrates are sitting nicely at 10 now but po4 dropped to .32.

What else can I do? Only have inverts and corals in the tank, no fish. I run a Hob filter with sponge filter pads, I took those out and cleaned them. Between those pads I have some matrix. So not sure what else I can do, maybe add more matrix and remove one of the pads?

X-37B · Jan 1, 2021

First I would retest. A 50% WC should have reduced po4 by alot more than .01 unless your source water is high in po4.
Phosgaurd in a mesh bag will do the trick. Use a small amount and go slow and check daily.

Biff0rz · Jan 1, 2021

90's reefer said:
First I would retest. A 50% WC should have reduced po4 by alot more than .01 unless your source water is high in po4.
Phosgaurd in a mesh bag will do the trick. Use a small amount and go slow and check daily.

I did retest, it was .01 lower. This is the same Hanna tester I use on my DT, which I just tested before the QT and it was where I thought it would be. So I'm thinking the test was accurate which is scary.

polyppal · Jan 1, 2021

Id go small amount of GFO

X-37B · Jan 1, 2021

Did you check your new salt water for po4?

Biff0rz · Jan 2, 2021

90's reefer said:
Did you check your new salt water for po4?

This I did not do (yet) but the DT uses the same source.

Biff0rz · Jan 2, 2021

Btw I have previously fed the inverts some algea disc's, my bet is that's the source of the po4...but I also thought a w/c would cut it down to a good level. I'll test again tomorrow and maybe another w/c

Biff0rz · Jan 2, 2021

Ok I tested again today... .32 again. I will test the source water later today. Then if that doesn't reveal anything then small amount of gfo. I have a 2lf phosban reactor, I can probably use that. If the source water is the issue, how do I fix that??

stanlalee · Jan 2, 2021

Rinse the matrix in old tank or new water, put a small amount bag of gfo or chemipure elite (bagged gfo and carbon) in the hob. Be careful as GFO can work too well if too much is used.

Biff0rz · Jan 2, 2021

stanlalee said:
Rinse the matrix in old tank or new water, put a small amount bag of gfo or chemipure elite (bagged gfo and carbon) in the hob. Be careful as GFO can work too well if too much is used.

Thanks. It's a 20L, how much gfo would you recommend? I've used it before so I know it's potent and don't want to bottom it out.

Uncle99 · Jan 2, 2021

Other than the number, is there any other reason you want to lower this number?
Sometimes it’s better to just leave it alone if it’s consistent, rather than destabilize for the sake of a number which is likely, not that accurate in the first place.
This tank runs at .25 phosphate.
Your only at .33......

Biff0rz · Jan 2, 2021

Uncle99 said:
Other than the number, is there any other reason you want to lower this number?
Sometimes it’s better to just leave it alone if it’s consistent, rather than destabilize for the sake of a number which is likely, not that accurate in the first place.

Whether it's accurate is one thing, but it's consistently accurate which I'm ok with. The thing is, my po4 in the QT is 3x what the DT is. I also get the whole don't chase numbers thought but at the same time I can't ignore how high it is. Corals don't respond immediately to changes so if I wait a week and they start to rtn I'll regret not changing it slightly. I assumed the w/c would have cut them in half at least, even consistently wrong.

stanlalee · Jan 2, 2021

Biff0rz said:
Thanks. It's a 20L, how much gfo would you recommend? I've used it before so I know it's potent and don't want to bottom it out.

I only use a table spoon on Rowaphos in a reactor for my 30g/10g sump and that brought phosphates from 0.33 to 0.03 in two days and I have 4 small fish fed daily. I'd probably start with like 2 teaspoons. The most I've ever used on my 30g is 4 teaspoons