Dosing nitrates (KNO3) to combat cyano

[syncro]

My tank
- 40G, over 1 year old
- 0 nitrates - probably because of the 3.5" deep sand bed
- livestock: anemones, soft/lps coral and 5 small fish
- macro algae will not grow
- cyano growing all over sandbed

I could use a phosphate remover but this will likely prevent any macroalgae growth and soft coral and LPS prefer some nitrates. So instead I'm thinking to increase nitrates so that macroalgae can outcompete the cyano. This is based on the redfield ratio idea - which seems to be more common in freshwater planted tanks and less so in reef tanks.

I'm thinking of:
- manually removing/cleaning all cyano
- adding chaeto
- dosing 0.5 mg/L daily, slowly increasing to 5 mg/L over a month

Thoughts? Thanks!

[FragIt Dan]

Why would you use Phosphate remover? Are your phosphates elevated? Are you assuming they are elevated because you have cyano?
First thing to do would be test phosphates. As for the Redfield ratio, are you trying to reduce phosphates or remove the cyano? I wouldn't necessarily interrelate the two. If your goal is to remove phosphates, GFO or analogous compounds will do the trick most simply and are a commonly applied solution. If your goal is to remove cyano, save yourself a huge hassle and start out trying ChemiClean. IMO, dosing nitrogen would be way down on my list of things to try.
On a side note, just because your nitrates are at, or close to zero, doesn't mean nitrates are not around and available for organisms to utilize, it just means they are being taken up as fast as they are being released. Right now your cyano might be using up the Nitrates more efficiently then other stuff in your tank. Were this the case, adding more nitrogen could bloom the cyano even more. I'm not saying this is the case, just one possibility. Start with chemiclean and if that doesn't work let us know and we can move to plan 'B' .


Dan

[kien]

Cyano? Chemiclean FTW!! :-)

[ckmullin]

I dose kno3 in a planted tank and it works wonderfully with plant growth. I'd be quite careful to dose something like that in a SW tank as you might also explode your Cyano growth!

If you want to enjoy an experiment dose kno3 in a small control tank away from your main display.

[Cal_stir]

+1 Chemiclean

[Borderjumper]

Originally Posted by Cal_stir

+1 Chemiclean

I used it for he first time last weekend... OMG it's the shiznit!

[syncro]

Thanks for the replies everyone.

Are you assuming they are elevated because you have cyano? First thing to do would be test phosphates.

Months ago when the problem started I tested at 0 phosphates. Yes I believe cyano is consuming all phosphates.

As for the Redfield ratio, are you trying to reduce phosphates or remove the cyano?

Remove cyano.

... start out trying ChemiClean.
Cyano? Chemiclean FTW!! :-)
+1 Chemiclean

Thanks for the suggestion. How does ChemiClean prevent cyano from returning? I am worried it is a temporary fix.

Right now your cyano might be using up the Nitrates more efficiently then other stuff in your tank.

Possibly! Is there anyway we can easily test this hypothesis against mine below?

My hypothesis is the DSB is starving the macro algae of nitrates and feeding the cyano with nitrogen. It is common for DSBs to reduce nitrates. I believe they work by hosting de-nitrifying bacteria which consume nitrates. A by-product of de-nitrification is nitrogen gas (my sand bed releases bubbles). Cyano is unique in that it can utilize atmospheric nitrogen. This could explain why the cyano grows well and prefers the sand bed while macro algae won't grow.

adding more nitrogen could bloom the cyano even more

Yes. I think it is critical to remove all cyano first (possibly using ChemiClean here). Then setting up an environment for macro algae to outcompete cyano - by dosing nitrates

[Reef Pilot]

Originally Posted by syncro

Yes. I think it is critical to remove all cyano first (possibly using ChemiClean here). Then setting up an environment for macro algae to outcompete cyano - by dosing nitrates

Actually, dosing carbon or using bio pellets will feed the cyano. You are correct, though, to first remove the cyano with ChemiClean. It works very well, if you follow directions. Then dose MB7 which provides beneficial bacteria to your tank, which out competes cyano.
http://brightwellaquatics.com/produc...robacter7t.php
It is not necessary to turn off your skimmer with MB7. Works great.

I would never intentionally add nitrates to a tank, given all my effort over the years to get rid of it.

[syncro]

Originally Posted by Reef Pilot

Then dose MB7 which provides beneficial bacteria to your tank, which out competes cyano.

Thanks Reef Pilot. I did try two weeks of full dose MB7. Cyano grew back even faster while dosing. Do you think I need to dose longer? The bottle is over a year old (though stored in the fridge and no expiry date listed) so maybe it isn't active now. The problem with MB7 is we don't know what bacteria is in it - what does the bacteria need to grow (carbon? nitrates? hamburgers?)

I would never intentionally add nitrates to a tank, given all my effort over the years to get rid of it.

I understand. My tank has had 0 nitrates since the cycle ended. I think because of the DSB.

[Reef Pilot]

Originally Posted by syncro

Thanks Reef Pilot. I did try two weeks of full dose MB7. Cyano grew back even faster while dosing. Do you think I need to dose longer? The bottle is over a year old (though stored in the fridge and no expiry date listed) so maybe it isn't active now. The problem with MB7 is we don't know what bacteria is in it - what does the bacteria need to grow (carbon? nitrates? hamburgers?)

Two weeks and stopping won't do anything for you. You have to keep dosing MB7, heavy for a couple weeks, and then tapering off, as per directions. I dose 1 cap every 3 or 4 days for a 100g tank on a permanent basis.

But to initially get rid of the cyano, you need to use ChemiClean. After that, the beneficial bacteria from your MB7 dosing should be taking hold. Of course other parameters need to be good as well, like P04 and KH (higher is better). And you need lots of flow in your tank. If there is any detritus in your tank, use a toothbrush to clean your rocks, and a turkey baster.