NW Cichlid Keith
For velocity:
flow rate in gallons per hour x 63 = flow rate in cm3 per minute
convert length and width from inches to cm by multiplying by 2.54
Length (cm) x width (cm) = surface area (cm2)
velocity = flow rate (cm3 / min) / surface area (cm2) = velocity (cm / min)
According to the papers the goal is 5-10 cm / min, though it seems to be very flexible.
D
dogofwar
a few things...
1) let me be clear, I have precisely ZERO actual experience with these filters, everything I have said has been an open discussion based on my research and my interpretation of things.
2) both Swiss Tropicals and Fish2Water disagree with you, they both say the mulm is where a significant amount of bacteria resides, and thus filtration occurs, and both of them say never to disturb the mulm.
3) yes, it has already been noted that cleaning these filters dumps a significant amount of stuff back in to the tank. The reason a traditional matten filter is not concerned with that is they clean rarely or never - so it just isn't an issue. If used at a significantly higher flow rate than generally recommended (in order to remove particulate better), thus requiring frequent cleaning, this may become a very large issue. However, one other thing I have read in a few places is you can do a decent job of cleaning them without removing them from the aquarium by going up and down them with a gravel vacuum / python / etc. This would only get the surface of course so you would still need to clean the inside eventually - but it could greatly increase the duration between needing to fully take it out and clean it.
My plan, which is certainly subject to change between now and acquiring the aquarium, is to set the higher flow / mechanical section up with variable speed powerheads. I would then experiment with the flow rate, aiming for the slowest possible flow that still kept the water clear of particulate. As a second tier to the experiment I would also divide the mechanical filtration sections into smaller zones. This would not only make cleaning significantly easier, but it will also allow me to purchase different pore size foam to test which works the best.
If the mechanical filtration fails spectacularly it would then be time for plan B. That could either be an internal box filter of sorts, putting up a divider where the foam is and converting it to an internal sump, or setting up some sort of external mechanical filter (canister, pressurized filter sock, bead filter, etc). One thing I need to decide I guess is should I order the tank with extra drilled holes to prepare for plan B...?