Stupid GFO Question

[Michael Rossi]

I'm running GFO and Carbon mixed. I put a small amount of GFO in relation to the directions as I heard it can quickly get you to 0.00. Its been about two weeks and I've noticed my phosphate levels start to rise. I thought the GFO would last me about a month.

Could the GFO have been used up quicker due to using a smaller amount than recommended?

1/4 Cup GFO and 1/2 Cup Carbon - 75 Gal Tank

 

[susan ingram]

Yep! Use the recommended amount, then adjust as needed. Hope that helps.

 

[Water Dog]

If you‘re mixing carbon and GFO together and you’re finding the the GFO is exhausting, then it’s a perfect time to switch out your media is carbon is pretty much useless and exhausts after two weeks as well.

 

[Fishingandreefing]

Do not use the full recommended dose especially you have sps. It will strip and kill them quicker then you think.

 

[SPR1968]

You might find it gets depleted quickly to start with as phosphate is taken up, but you need to change it as soon as phosphate rises about your target of say 0.03ppm or it won’t work effectively

just try and keep it locked down very low and you will avoid many of the issues you read about

 

[Michael Rossi]

Thanks for the feedback. I'm going to test it again today to make sure there wasn't something wrong with the reading and then i'll likely switch it out. I did go from around .3 to .1 so i'm sure that used up a lot of it. Thanks again!

 

[jda]

Study up on aragonite and phosphate binding. When you lower the amount in the water column, the aragonite will unbind phosphate into the water column - this can take a day or two. You will need to use more GFO to remove it. The aragonite can act as a reservoir for phosphate and can hold a huge amount - it binds to an exponential equilibrium with the water storing more and more as the water level rises.

It is paramount that you understand this if you want to do any kind of phosphate control.

 

[jda]

To best most effective with GFO, do not run it with GAC. Run a tiny bit and change it out every few days. The goal is to keep the P on a slow and steady downward path and not spike the water level down with too much GFO and then have it spike back up when the aragonite releases (and then do it all over again).

 

[Michael Rossi]

@jda I started to read up on this and am more confused than I started lol

I think what you are saying is that the GFO can basically only absorb so much phosphate. At some time when the phosphate stored in the GFO becomes more than what is in the water itself, the phosphate can be released back into the water, thus causing a phosphate spike and potentially an algea outbreak.

This would follow what I was experiencing. I started around .3 and got it down to around .15. Then it started to increase again. I think you are saying that the reason for the increase may not be that the GFO was "bad", but that the phosphate storage in the GFO became higher than what was in the water column and the GFO started to release phosphate in order to get back to more of an equilibrium???

Or am I completely off track? lol

 

[jda]

Kinda. Both aragonite and GFO bind phosphate to "equilibrium." If the water level goes it, it will bind more. If the water level goes down, then it will unbind some.

If you have a good amount in the water column, then there can be massive amounts in the rocks and sand. If you started with dry/dead rock, then there can be lots of bound terrestrial phosphate.

Use a little GFO and change it after a day or two for maximum effectiveness. So you lower the water column amount a bit, the rock unbinds a bit and then you start again. Don't use too much or else these swing can be massive and make corals mad over time. If you have a lot of bound phosphate, then you could need a lot of GFO.