Ultima touts their filters as "biomechanical"
http://www.aquaultraviolet.com/products/filters/ultima2/10000
I plan on using Ultima IIs for biological filtration on my small (compared to your tanks) 1700 gallon tank when it evenutally gets set up.
Thanks, Mom! Good to know. So they are pressure filters. Sounds as convenient as a filter can be! What are the cons?
I must take back my inkling on Vince's filtration. It's not thin at all then.
... One of my mistakes was using bulkheads that didn't allow enough water to pass... had to add a few more bulkheads because the pump was pushing more water than the drain could handle.
That's why I told you right away what GPH a 4" ball valve lets through at what head pressure - 15,000 GPH at 5' level differential, remember? Bulkhead would not be far off.
But the "smart" me is sitting in precisely the same puddle, as we say in a Russian proverb. My pumps cause my tanks to overflow because the drain size is too small + the sump is not low enough. I wish I used 6" bulkheads on my 4500 gals, instead of 4".