IMO, you should just start your tank with a refugium. I’ve had nothing but trouble with GFO. I lost many Corals to very large phosphate swings until I realized that it wasn’t a sustainable method of keeping a reef tank for me. Other people have success with it. Use of gfo creates a very inconsistent environment in the tank. If you don’t have any Corals in the tank, then use a lot of GFO, strip the water of all of the phosphates, your algae in the tank will most likely crash, then set up a refugium with a very bright light and let your tank stabilize. Carbon is also not very necessary for a healthy reef tank unless you have a die-off of some sort or a mass spawning. Corals need organics in the water, but you also want to maintain lower phosphate and nitrate. A well lit chaeto refugium will allow you to achieve both. Carbon and GFO are way too efficient at what they do.
