what does gfo, and carbon do?

[Reefing Madness]

GFO can do some weird things to a persons tank, if its just thrown in all at one time, some have said that corals and fish have died from the water quality getting all messed up. Its just safer if you ramp up the GFO, not just throw in the recommended dose for your tank all at once. Make sure your running it properly, and not at 1000gph through a normal filter, it won't work. It exhausts quickly if you have alot of phosphate in the system already, in a matter of days it needs to be changed and or recharged.

 

[alberthiel]

I use two small bags of GFO and two of Act Carbon, and only change one of each when I do the change that way the effect of the new GFO and carbon is not too strong all at once and will not affect the corals (esp) negatively

Changing too large a quantity all at once can suddenly drop nutrient levels too fast IME and that can affect the coral's well being FWIW