Okay, so if the coil being longer (and why is that bad) and there's more media (which implies a larger / bigger unit in order to facilitate the increased capacity) what WOULD make the thing BIGGER?
I mean, most of use larger capaity units than we need to increase processing, etc... so why is an overall larger unit not better?
I think ive answered this a few different ways now, but lets try another, you cant buy a stock ford ranger, and only put a bumper on it that will tow a 60,000lb trailer and say the ranger can pull a 60,000lb trailer that puny engine wont do it, the breaks wont do it, the transmition wont do it, it just wont work.
no one here in the last 3 pages has suggested building an overall larger unit, they keep thinking that extending the coil length alone is somehow better, ITS NOT also they keep making these huge bio chambers as if thats going to make it process more... it WONT a properly working and cycled unit removes all nitrate AFTER giving to any abrupt changes this is still a bio filter increasing the size of 1 part isnt going to make it better.
What size / configuration unit would you recommend for a 300 gallon system? kinda depends on the load, but you have choices, increase the ENTIRE size of the coil (not easy to do) or add more coils, for anything but HIGH bio load the easiest approach is to just add 2 or 3 coils to the same units. i know there is a simple table somewhere but 1/4"OD icemaker tubing is good between something like 50 and 75 feet, but 1/2"ID tubing needs to be over 250 feet to be opened up to anything making 1/2" tubing worth it and that is a LOT of tubing and a HIGH flow more than 300gph (for reference there is cheap 1/2" irrigation tubing available and its what ive used on breeding setups)
Also, how do you get nitrite and nitrate production in a zero oxygen environment? chemically ask a chemist i dont wanna dig thru papers to pull out the stuff. nitrate is produced in the coils as the oxygen is removed this is normal, however also normal is that the bio chamber has built up enought to process nitrate the increase from the coil is completely consumed. the nitrite is produced in 2 places normally in the coil, as those things that breethe oxygen are at work it can get thru the unit while cycling, and in the bio chamber when the bacteria in the chamber die.
Sorry.... I'm just confused. 
if your still confused please speak up