GFO color change.

[HighlandReefer]

Well this is a first for me. I just changed my GFO and carbon and have been doing this about once per month for a while now. My BRS HC GFO changed from the normal reddish color to a blue grey color. There was some build-up of a white material on the holding container inside surface, perhaps bacteria. The only thing I am doing different is dosing sugar, but I have been doing this for 1 1/2 months now. Would bacteria cause this color change?

The GAC looked normal.

[Marklu]

I could see that happening. I have heard of bacteria thriving in GFO reactors when individuals started carbon dosing. I don't know the mechanism of change color-wise, but I think its safe to say that this is bacteria related.

[Mike O'Brien]

When P binds to GFO it displaces a Hydroxide. What you are seeing is likely just abiotic precipitation from the high local pH around the GFO.

[tmz]

This happened to me with the high capacity gfo about a year ago. Randy, surmised it was localized precipitation of clacium carbonate and suggested I move my dosing site further away from gfo reactor inputs. I did; it worked.

[Randy Holmes-Farley]

I agree, it could be either, or both.

[HighlandReefer]

The pipe that draws water for the reactor is not in my sump where the kalk is added by a dosing pump. The same setup for well over a year. I suppose it must be the bacteria causing this, especially since I see a signififant build-up on the walls of the reactor now for the first time.

I would think that if it were calcium carbonate it would cause a whitish color, not the blue-grey color?

Never did this while dosing vinegar.

I have noticed that the water flow through the reactor almost completely stops now at the one month mark, which it never did before. Even when I open the 3/4" pvc valve all the way.

[Randy Holmes-Farley]

Put a little in vinegar and see if it bubbles.

FWIW, I have heard the CaCO3 deposits don't look white but can look more like you mention.

[HighlandReefer]

Well, I pulled the old GFO out of the trash and added some to vinegar. Fizz, Fizz ohh what a relief it is.

I learned something new today about the color of calcium carbonate. I assumed it would be white since dead coral is white.

Thanks for the help.

[Randy Holmes-Farley]

It may be white or clear, but on a GFO substrate it may look different. Maybe it also has a lot of iron in it. FWIW, iron carbonate is described as "gray, yellow, yellowish brown, greenish-brown, reddish brown and brown. Some specimens show an iridescence probably caused by surface alteration to goethite."

http://www.galleries.com/minerals/ca...e/siderite.htm

[HighlandReefer]

I looked at the gfo under my field scope. Can't get the camera to work with this scope.

There are blotches of grey & white deposits on the GFO.

Thanks Randy.

[HighlandReefer]

I decided to look at some new gfo (first I have looked at it under the scope). I did get my camera to work with the field scope after fudging with it:

New GFO:




Old GFO:



The old GFO has a very smooth glazing over it. It has taken on a completely different appearance.

[Randy Holmes-Farley]

If that is all CaCO3 coating it, it is almost certainly limiting its effectiveness.

[HighlandReefer]

I agree Randy.

The confusing thing to me, is I have been running GFO for over a year now with the same set-up (reactor and position in line in the system). The GFO has never looked like this when I changed it out. I have been dosing kalk in the same position in my sump for this period also. What a major change in my old GFO in one month and not doing anything different for months now (just sugar dosing).

[HighlandReefer]

I know my phosphate is very low, since I have been fighting Derbesia. The Hach PO-19 kit does not get any reading. Perhaps I will stop running GFO for awhile since dosing sugar to reduce the nitrates.

I still have nitrates at around 25 ppm and no Derbesia growth to talk about, so I am beginning to think that reducing the feeding drastically has controlled it. I had unreadable phosphate even when the Derbesia was out of control.

Maybe I am off basis, but I have slowly come to the conclusion that controlling ones feeding is the best way to control many algae problems.

PS: One way for me to see what effects phosphate has on microalgae problems will be to allow my phosphate level to creep back up a bit. This would eliminate phosphate from the issue.

[tmz]

I don't know Cliff mine(brs hc gfo)turned a blue grey; bit bluer than batlleship grey. It happened two or three times but never again and only in one of the two reactors I use. If I recall correctly I was dosing some extra baking soda near the pump input inadvertently at the time. I first thought it was from the sulfur dentirator but that was not the case.Great photos.