New to GFO Reacting. Advice before starting?

Christopher Poore · Oct 27, 2016

Hello Everyone!

I've been battling some phosphate issues for a while now and decided to purchase a GFO Reactor and GFO from BRS.

I have a 57gal tank with 25gal sump. Assuming 20% volume loss for rock and sand I have about 65 gallons of water volume.

How much GFO should I start with? Is there ANYTHING I should look out for while using the GFO? Color loss or anything in coral that would throw a warning sign that something is wrong?

How long do I keep the GFO in the reactor before replacing it? I read anywhere from 3-6 weeks?

Any other advice?

Thanks everyone!

Christopher Poore · Oct 27, 2016

BRS Calculator says 1 cup GFO. Should I start out with .75 cup to be on the safe side? I dont want to pull phosphates too quickly.

jsker · Oct 27, 2016

Run a phosphate test before you start, and run one 24 to 36 hours after you start the reactor to measure your drop. Yes you want a trace in the system for good coral health.

There is really no magic number to start with, and make adjustment after checking your numbers.

Christopher Poore · Oct 27, 2016

jsker said:
Run a phosphate test before you start, and run one 24 to 36 hours after you start the reactor to measure your drop. Yes you want a trace in the system for good coral health.

There is really no magic number to start with, and make adjustment after checking your numbers.

What sort of drop in phosphate would be too much of a drop? I think its currently at .07 but I will test again BEFORE running GFO and again in 24 hours.

jsker · Oct 27, 2016

Christopher Poore said:
What sort of drop in phosphate would be too much of a drop? I think its currently at .07 but I will test again BEFORE running GFO and again in 24 hours.

rule of thumb is no move than .05 ppm a day.

ksc · Oct 27, 2016

If you are at .07 you probably don't need GFO. Are you using the HC GFO or the regular stuff? I'd use about 1/4 of the recommended amount and see what happens. Dropping your value from .07 to .02 could cause STN if you have sps.

Christopher Poore · Oct 27, 2016

ksc said:
If you are at .07 you probably don't need GFO. Are you using the HC GFO or the regular stuff? I'd use about 1/4 of the recommended amount and see what happens. Dropping your value from .07 to .02 could cause STN if you have sps.

I am running SPS. I got the regular GFO.

I have been anywhere from .12-.07 without it dropping below .07 thus why I believe it's time to use the GFO.

ksc · Oct 27, 2016

With that water volume you might be better off doing a few 20-30% water changes. Keeping your po4 at .1 or lower should be fine. There aren't any hobby grade po4 test kits that can read your levels accurate enough to chase a number. Even the Hanna Colorimeter I paid $200 for is plus/minus .04.

hybridazn · Oct 27, 2016

Go with 1/4 cup to start and go from there, like previously stated going with too much could be bad for the system.

ksc · Oct 27, 2016

I usually run 1/4- 1/2 a cup in my 90 sps tank. I change out about once a month. It will immediately drop my po4 about .02-.03 but my po4's been running about .15 according to Hanna. Think in terms of percentages if you really want to drop it. Here's a good read:
https://www.reef2reef.com/threads/phosphate-that-is-evil-fear-that-is-real.252765/

reefguyty · Oct 27, 2016

I would suggest starting at less than a half a cup. I use BRS GFO as well and I use way less than they suggest. My system is about 400 gallons and my phosphates were .03ppm, I ran a 1/2 cup of BRS GFO and the phosphates dropped to 0 in a couple days.

Whenever I use the recommended GFO level it seems like my corals stop growing. I only run the GFO to pull the phosphates out then I stop using it until the phosphates creep up. I usually only run it for a couple days every six weeks or so.

jsker · Oct 27, 2016

When I go over .08 I start having issues, in fact I went up to a .16 and my corals were really not happy in the last two weeks and lost 7. Also check you No'3, they play a factor

Triggreef · Oct 27, 2016

Also i didn't see mentioned but gfo can & generally does drop your alk slightly so keep an eye on that. If you use a good amount of it then alk can drop quite a bit.