Do you run GAC on your SPS tank?

[penfold2]

I've always assumed GAC was a good thing for any tank, but after reading about the problems that some people have attributed to it, I removed mine today to see if it clears up some problems I've been having with a couple of corals.

I'm curious to see how many people use GAC, and what everyone thinks about its potential benefit or harm.

 

[Allmost]

what does GAC do ?

it will bond to DOC [Dissolved organic carbon] in water. and lower it to a certain point [depending on amount used per X gallon of water]. it will get used up, and over the course of 2 weeks to a month, DOCs might increase again, at which point it is wise to renew the GAC [so yo keep DOCs in a stable range].

now, above is how GAC is meant to be used, thee correct way.

if you run too much GAC, you will drop DOC too low, too fast, which will shock corals, and make them look more pale. if you do not exchange it when you should, it will make DOCs unstable, up and down, which again will stress corals, and the times of DOC drop would fade color of corals, decrease their health and so on.

from wht I have seen and read, all those cases happen when GAC is used incorrectly like explained above. I have never seen negative effect from using it correctly. I should note, that not all GAC are the same, some like the ROX are much more potent than others like KZ stuff or seachem's Matrix Carbon.

FWIW, I use GAC in all my set ups. if in passive flow,it will last a month, 1 cup per 100 g, if active in reactor, then half a cup , for 2 weeks. ...

 

[penfold2]

Interesting. I've never been a fan of passive use. It seems like the carbon in the center of the bag would essentially never get used if DOC's only get there by diffusion. Maybe with a larger particle size it would work better.

It sounds like flow rate could play a big part in proper use. I wonder if there is a good rule of thumb in terms of moving the system volume through the GAC x times per day.

 

[Allmost]

Interesting. I've never been a fan of passive use. It seems like the carbon in the center of the bag would essentially never get used if DOC's only get there by diffusion. Maybe with a larger particle size it would work better.

It sounds like flow rate could play a big part in proper use. I wonder if there is a good rule of thumb in terms of moving the system volume through the GAC x times per day.

using it passive, in a bag in the sump, you need to move it around once a day, to avoid channeling.

using it active, the flow should be low, the GAC should not move, as it will grind against each other and turn into dust/ash ....... which causes HLLE