No3 Po4 dosing gone bad, what should I do?


Manhattan Reefs
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I've been dosing 2 of my tanks with Red Sea No3 / No4 reducer for about 7 months. Lately I have been noticing blooms of purple cyano in my 36 gal tank and blooms of green cyano in my 72 gal. I also have had an ongoing problem with green hair in my 72 that I just cant seem to fix.

Lately, my Nitrate \ Phosphate tests have been showing near 0 for nitrate, and up to .75 for phosphates. I've been doing some reading and have found that its entirely possible for Red Sea No3/Po4 to bottom out the nitrates with high levels of phosphates. I suspect that is what i'm seeing right now.

I've seen some corals dying, and on of my amazing candy canes was overtaken with green hair, there wasnt anything i could do to save it. I recently purchased 4 turbo snails but they dont seem to be interested in either the green hair or the green cyano in my 72.

In my 36 gal, i have a stylophora thats been doing great for about a year, and still going strong. I also have a neon green monti, brown monti, and an alien eye challace. The challice was recently brought back from the dead when it started to die in a friends tank. All of them are still doing great in my 36 gal, but the green monti recently lost its vibrant colors and my cheto is dying at an alarming rate. in the past 2 months I'm down to about 10% of my original volume.

Obviously I'm going to stop dosing with the nitrate phosphate remover, and obviously i let my levels get out of whack without properly checking them. Thats my bad, I know. But, its been about 2 weeks since ive dosed the 36 gal, and ive cut back on dosing the 72 but still my nitrates read near 0 and phosphates up to .72.

My question is this, what should I do? I'm planning on doing a 15gal water change weekly for 2 weeks on my 72gal (30 gal total), and 10 gal weekly for 2 weeks on my 36. Will this be enough to fix my problem? Is there anything more that I should do?

Any help is appreciated. I'm sure you have more questions for me, please ask if you want more info. Thanks


Senior Member
Manhattan Reefs
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Manhattan, NY
Just add some Nitrate for 2 weeks and see if it doesn't get better. I think there's something to be said for just changing one variable at a time. I assume you have a good skimmer. Higher flow wouldn't hurt as well.


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First, try to find up , why your PO4 is so muck, 0.75 is like compare $ 75 to 2 Penney, you are a way up, most like it, is the food or RO/DI try to rise the food before you trow inside the tank, also RO/DI , check the PO4 right after your water filter.
In order to lower the PO4 you need to increase the Nitrate ( 2 ppm to 6 ppm) there is few ways to do that. To create a healthy system , you may need 0.02 to 0.05 ppm Nitrate and 0.02 to 0.05 PO4, Bacteria need both , stop dosing Carbon ( Vodka, Vinegar, Sugar , Vitamin C, the product you use. Do some water change ( Tropic Marine Pro is great salt) Feed less, try to find the source of PO4 , you introduce in your tank. If you got sand ? remember require some maintenance, increase water flow, run wet skimmer for few days , try Algae Scrubber or grow Chaetto , work great to remove PO4, but make sure , WHY your PO4 is so high ?!
Try to keep Alkalinity close to 8 or less.