I was close to that, but had to add a bit more when I restructured. But even with that little, NO3 has always been 0, so it's enough for filtration.

Yes, the fiji I bought is much heavier and less porous than the Pukani but I could not resist that good sale he had on the Pukani...:lol:

Do you still have your shallow sand bed Brad?

Can't forget the filtration provided by all those granules of sand as well. That's a lot of surface area right there.

You have a shallow sandbed also? I have to go back and look again.

I do in this tank, but did not in the last 2 setups. Same results either way.

Thank you! Very good point, I never thought of that

Yes. My sandbed is about 1/2 to 1". Simply for aesthetics but but the sand grains do provide surface area for biological filtration as well.

just how porous is epoxy? :biggrin:

+1 That's my understanding of that as well. You could put large non-pourous boulders and you wouldn't acheive very much filtration. When I go diving I study the reefs really close, and I've found the base of the reefs are very dense and then they become pourous as you ascend higher up the reef wall.

My Dad uses a ton of Rock but there are many spaces for caves, he went with lots of flat pieces rather than large boulders, his tank is over 10 years old...I've had better luck with pourous light rock myself.