GFO. How much, how often?

[mpderksen]

BRS dual reactor. 75 gal DT w/ 29 tall sump. Guidelines, if I can do the math, are to use a half cup of each GFO and carbon. Changing the GFO every two weeks, and carbon every four. Each tank is different, but does this sound about right? I'm using the ROX carbon and the standard BRS GFO.

I'm working through a GHA issue, so I'll likely change a bit more often until I get it under control, but it would be nice if there were an indicator when it was exhausted. I don't want to be putting $$$ in the trash by tossing it when it's still got some life left.

Michael

 

[Duvallj]

I test phosphates for checking to see if my gfo is exhausted. My gfo last anywhere from week to a month depending on how much I decide to feed.
Using guidelines are a good starting point but sometimes it has to be tweaked. Using recommended amounts of gfo kept my phosphates so low that my corals were not too happy. I just reduced the ammount and viola about 0.03-0.01mg/L.

As for carbon it is only useful for so long. I change my water every two weeks. So on the off weeks I change my carbon. As I see it the carbon would do the most good at this interval. BRS has a video of how each of their carbon performs. What I've seen was consistent with other studies that carbon is only good for about 1-7days depending on the carbon. The rox absorbs more, but taps out quick.

If you don't have one I would just pick up one of the hanna calorimeters as they are only about $50 and the reagents arn't that bad. I've checked my to a calibrated lab grade spectrophotometer and mine was right on (costs alot more). Not too bad for $50.

 

[TKCC]

Use 1 cup of GFO, and 1/2 cup of carbon. Change the carbon every 2 weeks, the GFO every month.

 

[mpjones]

What's the purpose of a calorimeter?

 

[mpderksen]

I believe he meant colorimeter. I actually sell UV/VIS specs, so have access to one. What wavelength do you use? Or do you use the reagents from the HANNA kit? I could go really crazy and use our GCMS, but I'd likely not make the lab guys very happy working on a personal method...