Sick and Tired! Endless Algae Problems

[SurfTrack]

Hi everyone.

I'm looking for some guidance on dinos and cyano in my 15g reef cube thats been running for about 5 months. My sandbed is practically infested and I'm getting desperate.

Tank: Setup on 7/30/25
- 15g cube
- CaribSea Live Sand + CaribSea Rock
- Refugium chamber seeded with live rock rubble
- Water Source: Distilled Gallon Jugs (2-3 TDS)
- Salt: Instant Ocean
- Water Changes: Weekly/Bi-Weekly 25% with Sand Vacuuming

Livestock: all healthy & active
- 2 clownfish
- 1 purple dottyback

Coral and Inverts: also healthy & growing
- Torch
- GSP
- BTA
- Leather corals
- Cleaner shrimp
- (5x) Bumblebee & (1x) turbo snails
- (1x) Emerald crab & (2x) blue-legged

Dino and Cyano Problem:
I've been battling both dinoflagellates and black cyano. Back in December, I viewed the algae under a microscope and I am sure I am dealing with cyanobacteria and dinos. However, I am less confident in the specific type of dinos but I believe them to be either Prorocentrum or Ostreopsis. I've attached the microscope photos below.

Back in December, I also dosed ChemiClean which completely wiped out the cyano...but that was followed by more dino growth.

This week, I'm seeing cyano start to return for the first time since the ChemiClean treatment. I also have seen a noticeable increase in copepods (which I took as a good sign)

My Questions:
1. Should I dose ChemiClean again to knock back the cyano?
2. Should I continue vacuuming the sand and doing water changes?
3. When I scrape the glass with a magnetic cleaner, am I just releasing more dinos into the water column?
4. How do I even begin approaching a solution for both dinos?

Finally, in terms of testing, I have API Master Saltwater and Reef Kits. I'm aware they aren't ideal but from what I've read it seems they can at least tell me if nutrients are bottomed out. What should I be looking for?

If anyone has any guidance/advice I'd really appreciate it! Happy to answer any questions or provide test results too.

 

[Hakon]

what's you're lighting setup like? none of those corals are particularly hungry for high PAR light so I might suggest dialing back your light, I'm currently dealing with cyano in my 38 about the same age as yours. Another suggestion would be nutrient export, maybe get a bit of fast growing decorative macroalgae that you can clip to get the nutrients out of the tank. Finally if your sand is infested get something that sifts it, I've got a tiger conch in my tank which does a great job, my sand sin't pure white but it's also not developing a mat either.

 

[Dom]

I'd like to know your chemistry numbers.

 

[slingfox]

If I were you I would replace all the rockwork. Oceanlive rock is preferred but pretty much anything other than CaribSea LifeRock is advised. Do a search on this board, CaribSea LifeRock is at the center of several endless algae battles. Maybe you can get these rocks to work long run. For Dino’s, you should refer to the many threads on this board on how to battle. Common suggestions are manual removal, UV, dosing silicate, dosing bottled bacteria, etc. Your tank is small but you likely want to get more snails to battle the algae which will come after the Dino’s are beat. Bumblebee snails are great but don’t do much algae eating.

See also this video:

 

[SantaMonica]

I have seen some live rock come from mining, not the ocean. This rock will have phosphate soaked in and leaking out for a while.

 

[SurfTrack]

what's you're lighting setup like? none of those corals are particularly hungry for high PAR light so I might suggest dialing back your light, I'm currently dealing with cyano in my 38 about the same age as yours. Another suggestion would be nutrient export, maybe get a bit of fast growing decorative macroalgae that you can clip to get the nutrients out of the tank. Finally if your sand is infested get something that sifts it, I've got a tiger conch in my tank which does a great job, my sand sin't pure white but it's also not developing a mat either.

I run my lights from 9:00 AM to 5:00 PM. Not sure the PAR but its an AI Blade and I have the settings to about 60-75%

 

[SurfTrack]

I'd like to know your chemistry numbers.

Just carefully tested with my API kit.

Phosphate: 0.25 ppm
Nitrate: >5.0 ppm (difficult to say given the limitations of this test kit, it could be reading zero which wouldn't surprise me)

 

[rtparty]

1) Don’t dose Chemiclean again. It helps for cyano but can hurt other things you need in the process.

2) Your rock isn’t the issue. I’ve got two tanks running CaribSea rock and the rocks stay perfectly clean. They aren’t leaching phosphate or anything detrimental.

3) Turn your lights down in half. For a 15g tank with an AI Blade you only need 10w of light at most. The MyAI app tells you a wattage. I believe Mobius does as well if you’re using that.

4) If possible, look into your own RO unit or possibly a different, better water source. Who knows what could be in the distilled water

 

[Idech]

Get a UV stick and use it while you are managing the rest. It will kill everything on the sand.

 

[141918]

Can you add your parameters for po4 and no3?

Ai blades are powerful. How tall is your tank?


The what looks like a dino on the one pic is round. Could be pro. Ostreopsis is unmistakeable as they literally look like an almond but 400 times smaller. Pro has a small circle in the middle of the cell. LCA have a sideways beak at the one end.

It's possible to have both cyano and dinos at the same time. To deal with cyano, nutrient reduction is recommended. However, having dinos, elevated nutrients are necessary.

 

[SurfTrack]

Can you add your parameters for po4 and no3?

Ai blades are powerful. How tall is your tank?


The what looks like a dino on the one pic is round. Could be pro. Ostreopsis is unmistakeable as they literally look like an almond but 400 times smaller. Pro has a small circle in the middle of the cell. LCA have a sideways beak at the one end.

It's possible to have both cyano and dinos at the same time. To deal with cyano, nutrient reduction is recommended. However, having dinos, elevated nutrients are necessary.

The light literally sits right above the surface. The tank is 15 inches deep.

My confusion is how to deal with cyano and also Dino’s. Aren’t the treatments opposite in terms of nutrients?

 

[141918]

Can you add your parameters for po4 and no3?

Ai blades are powerful. How tall is your tank?


The what looks like a dino on the one pic is round. Could be pro. Ostreopsis is unmistakeable as they literally look like an almond but 400 times smaller. Pro has a small circle in the middle of the cell. LCA have a sideways beak at the one end.

It's possible to have both cyano and dinos at the same time. To deal with cyano, nutrient reduction is recommended. However, having dinos, elevated nutrients are necessary.

The light literally sits right above the surface. The tank is 15 inches deep.

My confusion is how to deal with cyano and also Dino’s. Don’t the treatments opposite in terms of nutrients?

This is a tough one for sure. I had cyano, then used chemiclean then got LCA dinos. Right now I'm wining the battle with UV sweeper from 3D receding. Might be worth looking into. It won't do anything for your cyano, but will definitely kill the dinos.

Once your dinos are gone, then deal with the cyano naturally. Use diy coral snow and a good bacteria like microbe lift special blend. This will help bind it and you can remove it with skimmer

Do you have a par meter? If not, I'd get one. Ai blades are potent. My tank is the same depth. If you want, I can share with you my par chart so you have something to refer too.

 

[SurfTrack]

This is a tough one for sure. I had cyano, then used chemiclean then got LCA dinos. Right now I'm wining the battle with UV sweeper from 3D receding. Might be worth looking into. It won't do anything for your cyano, but will definitely kill the dinos.

Once your dinos are gone, then deal with the cyano naturally. Use diy coral snow and a good bacteria like microbe lift special blend. This will help bind it and you can remove it with skimmer

Do you have a par meter? If not, I'd get one. Ai blades are potent. My tank is the same depth. If you want, I can share with you my par chart so you have something to refer too.

That would be fantastic! Thank you!

I will also definitely be investing in a UV sterilizer.

 

[141918]

I would get a positive ID with a close up image. If it's Pro or LCA, you'll want the sand bed sweeper. If it's ostreopsis, a UV filter, 1 watt per 3 gallons will work.

Difference is that ostreopsis will go into the water column. Pro and LCA for back into the sand st night. It's reallt important to know which kind you have.

I will dig through my pics for the comprehensive par chart and report back. It's also located in one of my threads

 

[Idech]

I would get a positive ID with a close up image. If it's Pro or LCA, you'll want the sand bed sweeper. If it's ostreopsis, a UV filter, 1 watt per 3 gallons will work.

UV sweeper is cheaper (and a lot faster) and as long as there is brown crud on the sand, I would think it’s going to kill it. Just do it during the day.

 

[Dom]

Just carefully tested with my API kit.

Phosphate: 0.25 ppm
Nitrate: >5.0 ppm (difficult to say given the limitations of this test kit, it could be reading zero which wouldn't surprise me)

Yes, not the best test kit in the hobby.

I ask because I had a cyano issue recently. My scrubber completely stripped nitrates out; I was measuring zero.

I began dosing nitrates to the system, and after 10 days, the cyano was gone.

 

[Hakon]

I run my lights from 9:00 AM to 5:00 PM. Not sure the PAR but its an AI Blade and I have the settings to about 60-75%

That's good, AI's are really adjustable, I'm running a coralgrow blade on mine at about the same depth but with the risers (planning to swap to a hanging mount eventually). What I've noticed on mine is that it lets you go way higher on the whites which coincidentally are what algae thrives on the most, you might want to cut back on your white balance, also 9-5 is a fairly long light cycle in a new tank, I'm running mine 4-12 with 1 hour ramp up and ramp down programmed in the AI app and still seeing cyano though relatively slow growing. I've been doing some reading and seeing some literature saying that Cerith Snails eat cyano so I'm going to see if I can track some down tomorrow.

 

[Oldreefer44]

We need Alk, Ca , MG, PH and Salinity numbers from reliable test kits so that we can address the cause versus the symptoms. If you have a LFS nearby they should be able to do it for you. Your issue could also partly be a lack of desirable bacteria which is a common issue when starting out with dry rock.

 

[bbolin]

Still sounds like a young tank to me. Especially with any amount of dry rock. At ~5 months, a 15g cube is still biologically immature, and dinos + cyano often show up when the system is unbalanced rather than “dirty.”
Cyano and dinos are not signs of failure.
They’re succession stages.

At 5 months, your tank is still stabilizing biologically.


I would:

• Use pure 0tds RODI water moving forward
• Stop ChemiClean
• Stop sand vacuuming
• Pause water changes for 2–3 weeks
• Only siphon the worst patches if needed (into a filter sock)
• Run a small amount of carbon if possible
• Add more beneficial bacteria and pods wherever you can get them

 

[CHSUB]

Simple stuff, small tank! I have a 15 gallon freshwater tank that I have been neglecting and it was getting overgrown with hair algae. In about an hour did a larger wc, cleaned the algae, and “bam” beautiful tank again.

Stop with the nutrient stuff, chemical stuff, etc. 3 fed fish and you absolutely don’t have a nutrient deficiency. Add 6-8 algae eating snails, bumblebees are not; keep weekly maintenance up with manual removal and wc. It is that simple, there is no advanced calculus formula for algae only simple math: clean + reduced real estate for algae (corals) + consumers = no algae!