Is po4 swing bad in a WC?

Brian W · Jul 17, 2020

Will a major swing in po4 hurt sps or anything else in the tank? I plan to do two 25% water changes in the next few days. Tank is 50 gal TWV. I have 8-10 acropora frags and a couple that have a few branches. I have matched my new water to my tanks temp, sg, alk, cal & mag. I'm wondering if I should match po4.

Tank: PO4 - .32
New water: PO4 - .089

A little back story..
I have been battling Dinos for the past 2-3 months. I used Dr. Tims method 2 separate times. It helped but did not cure it fully. I did a WC and siphoned my sand. I then dosed no3 & po4 since my nutrients were very low (po4 .05 - no3 3ppm). Over the last month I noticed less and less Dinos. However in the past 2 weeks I noticed some hair algae growing the last 2 weeks. I was lazy and have not tested in the last 3 weeks.

3 weeks ago po4 - .10 and no3 20ppm.

Thanks in advance for the help.

Side note: frags are OP, WD, PC Rainbow, Pink Floyd, Garf Bonsai, Slimer, ASD Rainbow, Candlelight... Im sure they are all green due to high po4 & no3 ...but im working on coloring them back up.

Spare time · Jul 17, 2020

A drop is much less concerning than a sudden spike when it comes to waste levels. You should be fine.

Cory · Jul 18, 2020

I wouldnt worry about the drop in p04 hurting sps, but rather that dinos may get worse.

Randy Holmes-Farley · Jul 19, 2020

That particular change does not concern me. It will not drop nearly as much as you expect due to phosphate on rock and sand.

Why does your new water have that much phosphate in it?