hermaneb, if you still want to make the denitrator then it is very simple to constuct.
you need to get hold of some polycarbonate sheet (double walled stuff they use for greenhouses and the ilk), this can basically be any dimensions you want, like the back pane of the fishtank.....
if you have seen the polycarbonate before you will see that it is made up of squares...the idea is to cut a v shape into the bottom (leaving one for the outside) then into the top of the next, and bottom of the next and so on.....
if your following me you will see that when we put a hole into the side of the unit at the top of the outside wall, it will flow down and through the v, then up the next square, through the v and down the next square, through the v and so on.....
so once you have decided on the dimensions and cut your v's (except outer walls!) you can cut strips to be siliconed to the top and bottom of the unit.
next you want to put an inlet at the top of the unit, and an outlet (you can use ridgid airline) at the other end at the bottom.
the aim is to get about one drip a second out of the unit.....when the unit is full then you need to switch it off for about a week to alow the bacteria to colonise, then you can alow it to get back to the one drip.....test it in a bucket first to see how its doing with your test kit.....
any questions then just ask, but there are so many possibilities with these, some oxygenate the last few chambers, others make more compact units by cutting the last v of one strip in the side wall to allow water to pass into another strip...............
have fun anyhow! and if you need help with the idea then ask!
levi |