So I normally by Marineland GAC since it has good ratings and is fairly trouble-free except needing a lot of rinsing, but recently I let a guy sell me on his "Premium" Activated Carbon. He had a good story about how this pelletized carbon was made from premium carbon rather than the crap that Marineland etc. are made from:
Specs: "70 C.T.C 4.00 pelletized; 1000 - 1000 mg / gm iodine number; 3% moisture maximum, 10% ash maximum; 0.44 - 0.46 gm / cc apparent density; 1000 - 11000 m2 / gm specific surface area."
So here is what I did: I placed 1g carbon into 4g RO/DI water and soaked it for 1 hour. Then tested for PO4 and got a zero. So I thought to myself, Sherman doesn't know ****.
Then I let it soak for 24 hours. I also did a sample of Marineland side-by-side for comparison. After 24 hours I tested both and the pelletized had .06 mg/l PO4 and the Marineland had zero.
Then I poured out the RO/DI and re-filled for another 24 hour soak. At the end of that period pelletized = .06 mg/l and GAC = 0 mg/l of PO4.
Again I poured it off and refilled. 24 hours later, Pelletized = .08 and GAC = 0 mg/l PO4.
I repeated the pour and refill and once again tested after 24 hours and the pelletized = .11 mg/l and the GAC = 0 mg/l PO4.
Of course when I called he asked what the PO4 level of the RO/DI water was...duh...it was zero!! He said he had never had any trouble with it and that they had been selling it for years. I asked him if any of his customers had ever tested it for PO4 and he said of course since they sell it all over the place.
At any rate, I feel it doesn't really matter how much DOC a carbon can absorb, if it leaches PO4 into the system, and I have to wonder how many people around the country are using similar carbon and having nusiance algae issues.
Imagine you are having this problem...wouldn't your first thought be to change out your carbon?
