Who Gives A Fish Forums

My tank's been struggling with high phosphates lately, and my corals aren't looking great. What's the best phosphate remover y'all have used? I've got a 75-gallon mixed reef with LPS and SPS, running a protein skimmer and carbon. Parameters are stable except for phosphates sitting at 0.15 ppm.

I've had good luck with GFO in a reactor. It's gonna pull phosphates fast, but you gotta monitor it closely or it'll strip too much. Run it slow at first, maybe half the recommended dose, and check levels daily. What's your alkalinity sitting at? High alk can mess with how effective GFO is.

boomer wrote: ↑Tue Jun 17, 2025 7:53 pm I've had good luck with GFO in a reactor. It's gonna pull phosphates fast, but you gotta monitor it closely or it'll strip too much. Run it slow at first, maybe half the recommended dose, and check levels daily. What's your alkalinity sitting at? High alk can mess with how effective GFO is.

Agreed on the GFO. I'd also look at your feeding habits. Overfeeding's usually the culprit. Cut back on pellets and try rinsing frozen food before feeding. My phosphates dropped just from that.

GFO's solid, but if you want something gentler, try PhosGuard. It's aluminum-based, so some folks get sketched out, but I've run it for years with no issues. Just don't let it sit too long—swap it out every 3-4 days. What's your nitrate level? High nitrates can make phosphate problems worse.

I'm with flame9x on PhosGuard. It's chill and doesn't crash your levels like GFO can. Also, check your RODI water. If your membrane's shot, you might be adding phosphates with top-offs. Happened to me last year—took forever to figure out why my levels wouldn't drop.

How often do you do water changes? I bumped mine to 20% weekly and saw a big difference. Not a fix-all, but it helps keep things in check.

Y'all sleeping on lanthanum chloride. It's cheap and works like magic, but you gotta dose it carefully. I use it in a filter sock to catch the precipitate. Just don't dump it straight in the tank unless you wanna nuke everything.

FairyFish wrote: ↑Wed Jun 18, 2025 1:18 am Y'all sleeping on lanthanum chloride. It's cheap and works like magic, but you gotta dose it carefully. I use it in a filter sock to catch the precipitate. Just don't dump it straight in the tank unless you wanna nuke everything.

Lanthanum's risky business if you're not careful. I'd stick with GFO or PhosGuard unless you're really confident. Also, what's your lighting schedule? Too much light can fuel algae, which'll suck up phosphates and then release 'em when they die.

I've been using Rowaphos for years. It's pricey but lasts forever. Just toss it in a media bag in your sump. Also, how old are your bulbs? Old T5s can contribute to algae blooms.

Thanks for the tips, everyone. Gonna start with GFO at half dose and cut back on feeding. My nitrates are at 10 ppm, alk's at 8 dKH, and I'm running Radions for 8 hours a day. Bulbs are about a year old—maybe time to replace 'em.