I was just wondering, how much carbon is supposed to be used? a certain amount for each 5 gallons or something? Iv'e never been able to find out.

It really depends on what you want the charcoal to do for you.

Activated charcoal has a limited usefulness, for it has only a limited space to bind chemicals and nasties. After a time, it is "filled" and no longer useful. The small amount (1 tablesppon approx.) that you see in the pre-filled filter cartridges of the smaller filters (Penguin 150, 200 etc.) or the larger amounts of 2-6 T in the larger filters are calculated to last approximately 2 weeks. I generally do not use carbon in my filters under normal circumstances. It fills up so fast and ceases to do any good.

If you are using carbon to bind and remove medications, I read somewhere that it is suggested that you use approximately 1 Tablespoon per 10 gallons of tank water. This would need to be removed or changed after 24 hours.

I bought a container of carbon and it said to use 1/2 cup for every 10 gallons.

GOod grief! Where do they expectyou to put it?

That is certainly excessive!

That is what I thought too! I could only get 1/4 cup in my Top Fin 10. I haven't needed to change the carbon in my Whisper yet, but I am thinking since its so much bigger, I can probably fit 1/2 cup in there... I'll have to see though.....

Seem like I remember my carbon container saying something similar.
After reading up a bit on heavy metals and disinfection byproducts and looking at my city's water quality report, I'm beginning to think it'd be a good thing to keep fresh carbon in the tank regularly.

That sounds ominously scary!

The toxicity info I've found so far is in the "Cycling: Biofilter Bacteria, water quality, filtration" section.
http://dataguru.org/misc/aquarium/FishInfo.html#WaterQuality

Dr Tim has a good article on carbon
http://www.marineland.com/articles/16ActivatedCarb.asp

and here's a page on what carbon adsorbs.
http://www.wernersponds.com/Activated%20Ca...for%20Ponds.htm

Doesn't look like carbon does much with heavy metals. but it does suck up a bunch of other things to include the water disinfection byproducts (THM/Chloroform).

Thanks Betty,

Those articles are really good! I really enjoyed finding out about charcoal, it's one of those things that we kind of know is good for taking 'stuff' out of the aquarium environment, but exactly what and how much is never really explained properly..

Cheers!

It may be a balancing act to some degree. Per Walstad, the organics in the water help bind the heavy metals. Using carbon reduces dissolved organic compounds and could make metals more toxic. I am worried about copper in my tap water. on average it has 1.2ppm copper. I bought some poly filter that's supposed to remove it and plan to add that to the filter today. I'm also thinking about making my water harder as well since both copper and zinc are less toxic in harder water.