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padi200
10/05/2009, 08:57 PM
I saw the previous GFO question and mine is similar, but not the same so here it is.
I run a Two Little Fishies phosban 150 reactor for my 180 tank +40 sump and refugium.
I have found that this is not quite enough to control the phosphate in my tank unless I change the GFO pretty often. The 150 is only rated for 150 gallons, so this is not shock
NOW, TLF has a phosban 550 reactor that holds much more media and is of course much larger.

One major online seller said be careful because I am likely to put too much GFO in the reactor and that would "fry" my corals.
He could not explain how or why so my question is

IS THIS TRUE AND WHY?

Randy Holmes-Farley
10/06/2009, 04:42 AM
Yes, driving phosphate excessively low can be a problem.

How low is the phosphate now? Do you have an algae problem?

How long do you wait between media changes?

tatuvaaj
10/06/2009, 07:40 AM
IS THIS TRUE AND WHY?
That is the question! In my opinion it is unlikely that you can reach lower PO4 levels in an aquarium than in nature. The best test kits available to aquarists can only detect concentrations roughly 10x of typical annual mean for costal and inshore reefs, the minimum values are much lower.

Here is a nice table from "Schaffelke et al. Water Quality and Ecosystem Monitoring Programme Reef Water Quality Protection Plan. Final Report to GBRMPA. Australian Institute of Marine Science, Townsville (2007)"

http://www.reefcentral.com/forums/picture.php?albumid=121&pictureid=694

Maybe we are just not feeding our corals enough? Or maybe the use of GFO has something to do with the problems some people have reported?

padi200
10/06/2009, 07:42 AM
I do not measure the phosphates ( should I?). I just notice when I put in new GFO I have almost no algae problem, after about 3 weeks, the algae starts to grow a little bit. Nothing excessive.

Randy Holmes-Farley
10/06/2009, 08:35 AM
IMO, I'd replace the GFO a bit faster, about when the algae starts up. There is nothing magic about how long it lasts. It can be depleted in minnutes if phosphate is high enough, or much longer if it is low enough. :)

Randy Holmes-Farley
10/06/2009, 08:37 AM
That is the question! In my opinion it is unlikely that you can reach lower PO4 levels in an aquarium than in nature.

You do not believe that excessive GFO can drive phosphate too low? No matter how much you use?

I know that some folks think issues also relate to the rate of phosphate drops, but I do not really know if that is a concern or not.

tatuvaaj
10/06/2009, 09:55 AM
You do not believe that excessive GFO can drive phosphate too low? No matter how much you use?
Well, maybe if put one Acropora frag on top of huge GFO reactor :D

But no, in anything resembling a normal aquarium that can actually keep something alive, I don't think it is possible – or at least I don't until someone can actually show their aquarium water contains less than, say, 0.0002 mg/l PO4.

But that's really more like an academical question. For me the more interesting one is why some people seem to have problems when the phosphate drops below 0.03 mg/l which is clearly far more than in the waters the corals have evolved in?

Maybe the GFO actually strips too much bioavailable trace elements like Cu and Zn that corals need in very small amounts? One manufacturer (http://www.filtergranulat.de/index.php?cat=c36_DIAKAT--Adsorber-Granules-for-phosphate-removing.html&XTCsid=45815940f6a18a3893d6c79b934463b4) shows that some of these are removed very efficiently by the media. If most of these are already bound to organics in a typical aquarium, is it possible that the amount available to corals drops too low?

aquaman67
10/06/2009, 10:14 AM
One major online seller said be careful because I am likely to put too much GFO in the reactor and that would "fry" my corals.
He could not explain how or why so my question is

IS THIS TRUE AND WHY?

I think what he might be referring to, is when you are just starting out using GFO.

Phosban recommends that you start out using a small amount and gradually increase.

There have been problems with people who use GFO for the first time and use too much. Their corals have an adverse reaction to the sudden drop in PO4. I think this is what the seller was referring to. Since this new reactor is so large, it's easier to go over board. I think since you're already using GFO if you increase the amount over time, you'll be fine.