GFO or Chaeto

jmichaelh7 · Feb 6, 2026

On my new tank I am wondering if I should run Chaeto with a Kessil , or put some gfo in a reactor?

The tank is new a month old just wondering what is simplest route to maintain extra nutrients

exnisstech · Feb 6, 2026

What are your reasons for either? Some people run chaeto fuges to help with nutrient reduction. I run fuges to provide a place for pods and other small life forms to live and reproduce. GFO is good for lowering Phosphates but you don't know if your going to even need to worry about that. Kind of putting the cart before the horse so to speak. Refugiums can be beneficial in almost any system but not necessary IMO. GFO has a specific purpose which is to reduce PO4 and often is never needed.
If you do run chaeto it does just fine under a cheap grow light if money is a factor.

Randy Holmes-Farley · Feb 7, 2026

Both can work to export phosphate. The chaeto also exports N. Each has pros and cons. Neither is perfect.

This is my general recommendation:

Randy’s Thoughts on Nutrient Target Ranges

Thoughts on Nutrient Target Ranges by Randy Holmes-Farley Almost nothing in the world of reef aquarium chemistry causes as much discussion as selecting and maintaining ranges for nitrate and phosphate. Some aquarists want low targets, some want...

www.reef2reef.com

4. What targets seem reasonable? Of course, that depends on all the other factors at play, such as types of corals, availability of ammonia, particulate foods, etc. However, for a mature mixed reef, this would be how I personally would run it:

Let nitrate float between 5 ppm and 50 ppm. I’d use gentle export in this range, such as growing macroalgae.
Above 50 ppm, I’d begin to focus more on reducing it, by organic carbon dosing, turf or macroalgae, etc.
Below 5 ppm, I’d begin to dose ammonia or feed more. The target level might drop lower if dosing ammonia, just like the heavy in/heavy out scenario where nitrate may not be as needed.
Let phosphate float between about 0.06 ppm and 0.3 ppm. This range is higher than I’ve recommended in the past. I’d use gentle export in this range, such as growing macroalgae.
Above about 0.3 ppm, I’d begin to focus more on reducing it, by turf or macroalgae, or a binder such as GFO or lanthanum (has its own risks to tangs). If a binder: GO SLOW. Turf and macroalgae will typically be slow enough.
Below 0.06 ppm, I’d begin to dose sodium phosphate or feed more to get the level up.