Dosing nitrates (KNO3) to combat cyano
 

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!

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

Cyano? Chemiclean FTW!! :-)

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.

+1 Chemiclean

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

it's like sprinkling pixie dust in your tank. SO AWESOME.

Thanks for the replies everyone.

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

Remove cyano.

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

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.

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.

Proven method: Turn off your lights for 3 days, or only light the tank with blue light for 4-5 days (cyanobacteria do not absorb in the blue part of the spectrum). This is not long enough to harm corals, but the cyano will die off.

Reducing tank temperature to <74 F will also kill off most of it. I just noticed this in the last few months, when I gradually reduced my Q-tank from 80 to 73.5 F since the live stock were going to be transferred to a seahorse tank.

I highly doubt dosing nitrates will improve the situation. Nitrates are utilized by all algae, and the ones that grow the fastest will use it first... I would be afraid it could cause a hair algae bloom, or make the cyano worse.