GAC best practices

[LStorm]

Looking for guidance on current best practices for use of GAC in reef systems. I looked through the Reef Chemistry articles in the archive, but couldn't find what I was looking for.

I recently read and article promoting the idea of low flow in media reactors with carbon, on the order of 30 gph. Anyone here doing that?

Thanks.

 

[Randy Holmes-Farley]

I use ROX GAC from BRS in a canister filter, mixed with GFO.

if you use other brands, rinsing it may be very important to prevent things like HLLE in tangs.

 

[LStorm]

Randy, do you know what kind of flow rate you have throught the canister filter?

Oh, and do you run carbon 24/7?

 

[Randy Holmes-Farley]

Not sure, but I'd guess it is something like 1-2 gallons per minute. It is a Magnum canister that I won at a MACNA years ago.

Yes, I run it 24/7.

 

[LStorm]

Thanks Randy

 

[FrankMcD]

good info

 

[maysorum]

I use ROX GAC from BRS in a canister filter, mixed with GFO.

if you use other brands, rinsing it may be very important to prevent things like HLLE in tangs.

Do you use layers? Or mixed together? If layers, which one is on the bottom and does it matter?

 

[bertoni]

There's no need to mix them, and the order doesn't matter very much, most likely, but I might put the GAC first, to remove as much organic content as possible, so that it doesn't foul the GFO quite as much.

 

[bellis31]

I run GAC and GFO in my TLF 150 with GAC on the bottom then a sponge and the GFO on top, seems to work well. I crank up the flow until I see the GFO on top move just slightly!

 

[LStorm]

I recall reading an article some time ago that advocated low flow rates for carbon filtration, I believe it was Spotte that promoted the idea. Flow rates on the order of one tank volume per day... Yes, per day not per hour.

Anyone do this out there?

If carbon filtration is most effective at low flow rates, then use with GFO would seem to be contraindicated.

 

[Randy Holmes-Farley]

Do you use layers? Or mixed together? If layers, which one is on the bottom and does it matter?

I mix them together, then after a week, I take it all out, rinse and mix it again, and then after another week, I toss it and start over.

 

[Randy Holmes-Farley]

I recall reading an article some time ago that advocated low flow rates for carbon filtration, I believe it was Spotte that promoted the idea. Flow rates on the order of one tank volume per day... Yes, per day not per hour.

Anyone do this out there?

If carbon filtration is most effective at low flow rates, then use with GFO would seem to be contraindicated.

Depends on how you use it.

Low flow is clearly best in a single pass application, but in a recirculating use (like we all use), higher flow is the same or better (IMO) in terms of organic binding as long as you do not cause channels to form where the water does not contact the GAC. The rational is simple: make sure the GAC is being exposed to the dirtiest water possible, and higher flow brings that dirty water into it more rapidly than does low flow where the water gets cleaned up and some of the GAC (the most downstream part) is seeing cleaner water. That effect is probably small, however, and it probably does not make a big difference as long as you are using reasonable flow.

Other issues include the potential for higher flow to collect more detritus if the GAC is not tumbling. Another is tumbling GAC too hard breaks it and releases fines. I would not want that.

 

[jerpa]

I run both in the same reactor. I mix them together. I thought I read somewhere that the reason for tumbling GFO was to stop it from clumping. Because I have carbon mixed with it I dont have this problem and as stated above I don't want my carbon to tumble. I run my reactor off my return so I don't know the exact flow but I would say it's a few gallons per minute.

 

[LStorm]

OK, makes sense. Thanks for all the input.