Grow Algae Instead Of Cyano


Trying to grow algae (particularly chaeto and hair algae) instead of cyanobacteria.
  1. Does cyanobacteria prefer higher or lower lighting than algae (i.e. watts per gallon)?
  2. Does cyanobacteria prefer higher or lower spectrum lighting than algae (i.e. kelvin)?
  3. Does cyano prefer longer or shorter lighting duration than algae (6-12 hrs)?
  4. Does cyanobacteria prefer higher of lower flow rate than algae (15x - 50x)?
  5. Does cyanobacteria require any nutrients that algae does not that I could remove?


I'm trying to figure out... are you having cyanobacteria issues?

But from what I've come across is usually people that have cyanobacteria also run into the Redfield ratio. Where your Phosphate ratios are higher than Nitrates.
  • Thread Starter


Thanks Nart,

Yes, I am having Cyanobacteria issues. Instead of growing cyano I want to be growing my chaeto (in display tank) and hair algae (so I don't have to supplement feed my blennies as much). With the 5 questions above, I am trying to figure out what conditions grow algae compared to cyanobacteria.

- Lighting watts per gallon: low intensity
- Lighting spectrum: 560-620nm (lower spectrum)
- Lighting duration: Greater than 8-9hours
- Flow: Low
- Nutrient requirements: Phosphates, Docs, Nitrates

Hair Algae
- Lighting watts per gallon: doesn't seem to be a major factor
- Lighting spectrum: doesn't seem to be a major factor
- Lighting duration: doesn't seem to be a major factor
- Flow: not mentioned
- Nutrient requirements: Nitrates, Phosphates

Cultivating MacroAlgae
- Lighting watts per gallon: High
- Lighting Spectrum: not mentioned
- Lighting duration:not mentioned
- Flow: moderate to high
- Nutrient requirements: Nitrates, Phosphates

So it seems that if you want to grow hair algae or chaetomorpha instead of cyanobacteria, one option is to increase flow.....currently my flow rate is already high though (around 40x).

Nart, the redfield ratio article is great: "The theory holds that green algae do better at high ratios. Ratios less than N: P / 5:1 (little nitrogen, phosphorus much) often give to cyanobacteria see a clear trend." So reducing phosphates would encourage more growth (as would organic loads). Additionally dosing iron and calcium can help algae growth.


I'm glad I was able to give you some info that was able to help.
Looks like you've done a bit of research too.

If it were me, I would focus on tackling the cyano first as that can be a pain to get rid of. But be persistent and you'll eventually win.
Good luck.
  • Moderator


My understanding with freshwater planted tanks is that cyano is caused by excess organics not phosphates or nitrates. I would think that its the same as a saltwater tank.

I'm just now almost finished dealing with an outbreak that only started when I introduce a heap of emerses plants to my tank.

I haven't changed anything in my fert or lighting schedule, still only do 1 25% water change a week. Just removing organic waste has stopped the growth and over the last 2 days its started to die off.


smee82 Not the same as freshwater. I posted a PDF article that explains the Redfield Ratio of N and P. If you're curious, read it too.
Most of the saltwater hobbyists that I run into that have Cyano issue also have an imbalance of N to P. In most cases within freshwater, the rocks and wood do not leach phosphate.
Whereas in saltwater, typically reefers who uses dry reef rocks and do not properly cure it will run into with excess phosphates leaching. This quickly causes an imbalance of N and P. Paired with lighting intensity, and low flow in some areas can quickly cause an outbreak of Cyano. Though, I'm not saying this is the exact issue with the OP's post, just simply pointing out that it is not the same as freshwater.

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