i personally think that they would be very easy to keep.
Not really
. In this type of layout you don't have a lot bio-mass like in other aquascapes with fast-grow plants like rotalas, hygrophila etc. With 2.5-3.6WPG over iwagumi tank you could have problem with stabilisation micro and macro. IMO iwagumi is very hard to keep if we speak about "water condition" but easy if we speak about layout (time progres). I have over month old iwagumi layout(java moss, eleocharis) with only 1.4WPG and sometimes i have small problems with algae (specially GSA and BBA on rocks)....
