phosphate issues in reef tank

LPS, SPS and all coral chat
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crafton
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Joined: Wed Oct 09, 2024 9:40 pm

phosphate issues in reef tank

Post by crafton »

My reef tank's been acting up lately, phosphate levels are through the roof. Got a 75 gallon with mixed LPS and SPS, running a protein skimmer and carbon. Anyone got tips to cut it down without nuking my corals?
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florapen
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Joined: Sat Jan 07, 2023 8:18 am

Re: phosphate issues in reef tank

Post by florapen »

Been there. What's your water change routine? If it's sketchy, that's likely the culprit. I had the same issue in my 120 until I bumped changes to 20% weekly. Also, check your RODI water—sometimes the filters go bad and leach phosphates.
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_fluxer
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Joined: Sat Aug 03, 2024 8:21 am

Re: phosphate issues in reef tank

Post by _fluxer »

Yep, RODI's a big one. Test your makeup water first. If that's clean, maybe cut back on feeding. I was overdoing it with frozen mysis, and my phosphates spiked hard. Switched to pellets and it chilled out.
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darktank
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Joined: Thu Oct 10, 2024 8:59 pm

Re: phosphate issues in reef tank

Post by darktank »

florapen wrote: ↑Mon Jul 21, 2025 8:13 pm Been there. What's your water change routine? If it's sketchy, that's likely the culprit. I had the same issue in my 120 until I bumped changes to 20% weekly. Also, check your RODI water—sometimes the filters go bad and leach phosphates.
Second this. My RODI was dumping phosphates for weeks before I caught it. Now I test it monthly.
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aqualuna
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Joined: Wed Oct 09, 2024 9:52 pm

Re: phosphate issues in reef tank

Post by aqualuna »

If all else fails, grab some GFO. It's pricey but works like a charm. Just don't go nuts with it—dose slow or you'll shock your system. I run it in a reactor for a couple days, then pull it.
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frostmix
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Joined: Mon Jun 19, 2023 1:22 pm

Re: phosphate issues in reef tank

Post by frostmix »

What's your nitrate level? High phosphates usually pair with high nitrates. If both are up, you might have a nutrient export issue. Look into chaeto or a refugium if you don't have one.
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microsis
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Joined: Thu Oct 10, 2024 9:04 pm

Re: phosphate issues in reef tank

Post by microsis »

GFO's solid, but if you're skimping on flow, it won't matter. Make sure your powerheads are pushing enough. I upgraded to a pair of MP40s and my phosphates dropped just from better circulation.
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sandie
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Joined: Wed Oct 09, 2024 9:32 pm

Re: phosphate issues in reef tank

Post by sandie »

I'm new to this, but my LFS said overfeeding's the biggest cause. They told me to feed half what I was and see. It worked! Maybe try that before dropping cash on gear.
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oceanite
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Joined: Tue Mar 19, 2024 10:56 am

Re: phosphate issues in reef tank

Post by oceanite »

crafton wrote: ↑Mon Jul 21, 2025 6:57 pm My reef tank's been acting up lately, phosphate levels are through the roof. Got a 75 gallon with mixed LPS and SPS, running a protein skimmer and carbon. Anyone got tips to cut it down without nuking my corals?
How old's your rock? Old live rock can leach phosphates for years. If it's ancient, consider swapping some out or cooking it.
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jilly
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Joined: Wed Oct 09, 2024 9:32 pm

Re: phosphate issues in reef tank

Post by jilly »

My tank's small, but I had luck with phosguard. Just tossed a bag in the filter. It's cheaper than GFO and worked for me. Maybe worth a shot?
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