High Phosphates, zero Nitrates (FOwLR) - Should I dose nitrogen to stimulate Chaeto growth to lower phosphates?

[chadfish]

I have a 60 gal FOWLR tank (for the moment) with Cheato in the refugium of a 20gal sump. I have high phosphates (API reads .5 ppm) but 0 nitrates.

I've read that Chaeto is NO3 limited. Should I dose nitrogen so the Chaeto will grow faster and eat more phosphates?

Or should I just continue to use PhosGuard to lower Phosphates and go from there?

 

[Randy Holmes-Farley]

I would dose nitrate to avoid dinos, if nothing else.

It may also help bring down phosphate.

 

[Tired]

Why do you want to lower phosphates? They aren't directly harmful to livestock in pretty much any amount you can reasonably hit. There are reef tanks with 1ppm+ phosphates, never mind FOWLR tanks.

You definitely need the nitrates up, though, to avoid the aforementioned issue with dinos.

 

[chadfish]

I’ve had a rough go with cyano and other algae due to high phosphate. Don’t want a repeat.

I cut back the chaeto by 1/2 and started dosing nitrogen. After the new year, I’ll add more stock, that will help keep the NO3 at a healthy level.

 

[blasterman]

High phosphates / zero nitrates is a bomb waiting to go off.

 

[chadfish]

What should I do about it?

 

[Tired]

Add nitrates.