Cyano in 2 year old tank?

Floyd- · Jul 15, 2025

Ive had my tank setup for over 2 years and now im battling cyano out of no where. Red slime with bubbles. I tried chemi clean per the directions and it didnt touch it in 48 hours. Tank is a IM25 Lagoon.

Last tests a week ago were:
Temp-78
Salinity- 35ppt
Nitrate-1.1ppm
Cal-360
Mag-1230
Alk-7.1
Phos-.09

All hanna tests other than cal and mag. Those are salifert. The only thing thats changed recently is switching from All 4 reef to just baking soda for alk.

Utubereefer · Jul 15, 2025

Got pictures of the tank and equipment list?

EricR · Jul 15, 2025

Same thing happened to me at about the 3 year mark -- never saw a spec of cyano then, suddenly, a bunch mostly on the sand.
No idea why since I didn't change anything or have any parameter shifts.

Mostly under control now after many months of just living with it.
I wasn't really aggressive with any tactics so basically just went with:
- manual removal -- turkey baster to blast off sand, try to suck up, syphon through fine net.
- calcium carbonate dosing (DIY coral snow) helped but I could've been more consistent with doing it.
- started dosing PNS Probio a couple of times a week and, perhaps coincidentally, seemed to have a dramatic effect (unless it was just mostly timing along with everything else).

Check this out if you haven't seen it, regarding calcium carbonate dosing:
Cyano Eradication

Floyd- · Jul 15, 2025

This was from about 2 weeks ago right before the cyano took off.
Reefbreeders 24" light at 50% blues. 2x nero 3's at 50% max with random mode. No skimmer just filter socks and a UV light.

Randy Holmes-Farley · Jul 15, 2025

unlike most other pests, cyano can consume organics readily, so exporting more organics can help reduce it. There are many ways, such as water changes, GAC, skimming, coral snow, purigen, polyfilters, and not dosing organic carbon.

More flow also often helps.

EricR · Jul 15, 2025

Randy Holmes-Farley said:
... cyano can consume organics readily...

Interesting note,,, thank you.
I've never owned a skimmer and noticed OP said "no skimmer" as well.

JTP424 · Jul 15, 2025

Livestock looks healthy so that's a plus!
Any changes regarding the tank environment? Opening windows more, more natural light etc?

X-37B · Jul 15, 2025

In my 170 cyano was eliminated by increasing the flow. I had flow set for a year and now just increased it and it's gone.
In my 15g I could not increase the flow so I did chemi clean waited 2 days and dosed again. Completely gone now.
Best advice is physically remove the cyano. Stir it up and use a net to remove as much as you can before you start then continue removing it daily until it's gone.
If you don't physically remove the cyano it makes it difficult to complelty remove.
A second dose may be needed.

Floyd- · Jul 15, 2025

EricR said:
Interesting note,,, thank you.
I've never owned a skimmer and noticed OP said "no skimmer" as well.

Never needed one and on this small tank it was always mainly water with little to no skimmate.

JTP424 said:
Livestock looks healthy so that's a plus!
Any changes regarding the tank environment? Opening windows more, more natural light etc?

Nothing. No lights other than tank lights in the day normally. I have blackout curtains to avoid natural light issues. Only thing thats changed of late was going from A4R to baking soda.

X-37B said:
In my 170 cyano was eliminated by increasing the flow. I had flow set for a year and now just increased it and it's gone.
In my 15g I could not increase the flow so I did chemi clean waited 2 days and dosed again. Completely gone now.
Best advice is physically remove the cyano. Stir it up and use a net to remove as much as you can before you start then continue removing it daily until it's gone.
If you don't physically remove the cyano it makes it difficult to complelty remove.
A second dose may be needed.

This is my second dose so far. Today will be the end of that 48 hours and I bet there is a ton of red when I get home in a little. Ill keep basting it and keeping the flow up and the socks cleaned.

X-37B · Jul 15, 2025

Floyd- said:
Never needed one and on this small tank it was always mainly water with little to no skimmate.

Nothing. No lights other than tank lights in the day normally. I have blackout curtains to avoid natural light issues. Only thing thats changed of late was going from A4R to baking soda.

This is my second dose so far. Today will be the end of that 48 hours and I bet there is a ton of red when I get home in a little. Ill keep basting it and keeping the flow up and the socks cleaned.

Just keep removing it.
I also did not do a WC between dose 1&2. And only 10% 2 days after #2.
Looks like you don't run carbon.
That will help wtth no skimmer.
I use 2 chemipure blue nano packets in my 15 which is 2× what's recommended. I like the blue with the resin for my nano and use rox in everything else.