cyanobacteria in coral tank woes

LPS, SPS and all coral chat
trailblaz0r
Posts: 4
Joined: Thu Oct 10, 2024 9:49 pm

cyanobacteria in coral tank woes

Post by trailblaz0r »

Been battling cyanobacteria in my 75g mixed reef for weeks now. Tried manual removal, reduced feeding, even blackouts, but it keeps coming back. Running two AI Primes, 0 ammonia, 0 nitrite, 5 nitrate, 8 dKH. Any long-term fixes that won't nuke my Acros?
dunamis
Posts: 2
Joined: Thu Oct 10, 2024 6:34 pm

Re: cyanobacteria in coral tank woes

Post by dunamis »

Had the same issue last year. What's your phosphate level? Cyano thrives when there's an imbalance between nitrate and phosphate. If it's undetectable, try dosing NeoPhos to 0.03 ppm while keeping nitrates around 5. Also, increase flow in dead zones with a cheap wavemaker.
clawmaster
Posts: 2
Joined: Thu Oct 10, 2024 10:06 pm

Re: cyanobacteria in coral tank woes

Post by clawmaster »

dunamis wrote: Fri Jun 06, 2025 3:46 am Had the same issue last year. What's your phosphate level? Cyano thrives when there's an imbalance between nitrate and phosphate. If it's undetectable, try dosing NeoPhos to 0.03 ppm while keeping nitrates around 5. Also, increase flow in dead zones with a cheap wavemaker.
Yep, flow's key. I added a Jebao SLW-20 to my back corner and cyano cleared in two weeks. Just don't go ham with the GFO, or you'll crash your phosphates again.
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alohavibes
Posts: 3
Joined: Thu Oct 10, 2024 12:18 am

Re: cyanobacteria in coral tank woes

Post by alohavibes »

My 40g breeder had cyano after I switched salts. Tested everything, turned out my RODI filter was shot. TDS was 12. Replaced the cartridges and did three 20% changes over a week. Cyano's gone now. Maybe check your water source?
mander
Posts: 4
Joined: Fri Mar 22, 2024 8:41 pm

Re: cyanobacteria in coral tank woes

Post by mander »

Seconding flow adjustments. Also, what's your cleanup crew like? I added 10 more Trochus snails and they graze on the cyano film. Not a full fix, but helps between water changes.
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copperkit
Posts: 18
Joined: Tue Feb 01, 2022 10:25 am

Re: cyanobacteria in coral tank woes

Post by copperkit »

Weird vibe, but my cyano vanished after I stopped using Brightwell CoralAmino. Started dosing AcroPower instead. Dunno if it's coincidence, but maybe check your additives?
trailblaz0r
Posts: 4
Joined: Thu Oct 10, 2024 9:49 pm

Re: cyanobacteria in coral tank woes

Post by trailblaz0r »

Thanks for the tips, all. Phosphate was 0.01 last I checked. Gonna test the RODI, bump flow with an old MP10, and grab some Trochus snails this weekend. Will report back.
dolido
Posts: 5
Joined: Mon Apr 25, 2022 7:30 pm

Re: cyanobacteria in coral tank woes

Post by dolido »

My LFS said cyano's normal in new tanks. Mine's 4 months old. Should I just wait it out?
dunamis
Posts: 2
Joined: Thu Oct 10, 2024 6:34 pm

Re: cyanobacteria in coral tank woes

Post by dunamis »

dolido wrote: Fri Jun 06, 2025 10:26 am My LFS said cyano's normal in new tanks. Mine's 4 months old. Should I just wait it out?
Nope, that's a myth. New tanks get diatoms, not cyano. If it's red and slimy, act now. Check your nitrates, phosphates, and flow like we've been saying.
airtys
Posts: 2
Joined: Thu Oct 10, 2024 9:09 pm

Re: cyanobacteria in coral tank woes

Post by airtys »

I used ChemiClean once. Worked fast but my Zoas closed up for days. Wouldn't recommend unless it's real bad.
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