Lets take a look at the thought process here. If you go with a wet/dry and you use bio balls, we know that the balls are very efficiant at breaking down the very toxic to the least toxic ammo>trites>trates, and this is where most have a DSB, Fuge, nitrate coil, or some plan to export or use up the nitrates. The balls are also very good at oxygenating the water as well, very good due to the round shape and tiny little spikes on them.
Main complaint here is that eventually the bio balls will get clogged with debris and raise the nitrates, which can be cured with simple maintance, btw.
I took a look at the link and saw square dead coral peices. It would have helped to expand the pic to take a better look at the squares to see how porous they were but letts say that they were very porous, full of nooks and crannies, and looked good.
Now if you use them in the same manner as you would bio balls in a trickle method what would happen.
This is my OPINION --
Would they house the benifical bacteria.....Yes
Would there be as much surface area vs. bio balls.... I don't believe so,. no way.
Would they be as good at oxygenating the water.... No way.
Why? Lets take a look at the shape of the balls vs. the squares here for a moment. Ever notice that nature tends to make things round? A square boulder will even become round given enough time. Rocks in a river bed become smooth and rounded. A drop of water, even the atoms and electrons that form that drop of water are rounded. Even the earth is round. This is one reason why we like sand rather than crushed coral. An ounce of sand will have more surface area than an ounce of CC.
Round is natures way of giving something that will have the most amount of volume with the smallest amout of space. Sure that doesn't help stack leftovers in the fridge but you get the idea.
So what I am saying is that the round shape vs. the square, round will offer much more surface area, more surface area will result in more filtration and a higher bio load capacity.
The more surface area offered by the bio balls will also allow the water to cover more surface area, the spikes on the balls will also help to break up the water and cover more area. The more the water is exposed to surface area the faster the reaction time for it to convert the ammonia down into nitrates. You can't beat that with squares or even rock rubble.
On the clogging problem, both the balls and the squares/rock rubble are going to have the same problem here. They will get dirty, if they get dirty they will have to be cleaned, its going to be alot easier to clean the balls, how are you going to get the junk that has formed up in the middle pores of the square? It can be done but it will most likely take more maintanance.
Does all this mean that the square rock will not work.. No but why would you want to use something what will reduce your surface area, reduce your oxygen, and require higher mainanace
If your not gaining anything why reduce your benifits.
I think if you were to submerge the rocks instead and let the water flow through them instead of trickle, then you would have a more natural way of filtering and you could maybe maintain them better, like the turkey baster thing to clean them off, but since they are small and square you can just rinse them like bio balls. Live rock in the sump is a good idea for extra filtration.
Well I might as well get off of my soapbox, I didn't draw much of a crowd anyway.
Thomas
