Use of 2 medias in 1 reactor

[whatcaneyedo]

GFO wont necessarily be used up before the carbon. That all depends on what your present phosphate level is. If its quite high the GFO could become saturated within a couple of days. The same can be said about carbon. If your tank has a lot of dissolved organic compounds, a high bioload and the water is quite yellow the carbon could become clogged pretty fast.

The whole argument of how much to use and when to change it give me a headache. My own advice is to start off using a minimal amount of each and adjust if necessary.

I personally just use one cup of each in separate TLF reactors which I change out monthly on my 220gal system. The water is extremely clear and phosphates have been undetectable with simple test kits for the past two years. The reason I keep them separated is because I dont want too much flow through the carbon which would cause it to fluidized and grind together to create fines. But I do want just enough flow through the GFO to create a little bit of agitation at the surface because that is what the manufacturer recommends. For me this seems like the optimal way to do things.

This topic has been discussed a few times before. Try doing a search and you'll find much more information.