stag and clado - mulm under cuba?

[fourmations]

hi all

this could be a a filtration topic but here goes...

i have bunches of stag and plenty of clado
coming up through my cuba

when a largish portion of cuba became uprooted
i noticed a lot of mulm under it
(there was so much, i could not see the substrate)

I have a mate who's cuba also became uprooted and
he says there was no visible mulm
(but having said that, i have light coloured gravel and he uses AS
so it would not be as obvious)

is this mulm normal or have I issues

my filter is a fairly beefy eheim
(1050lph on a 100l tank)
i have wrapped the strainer since I got shrimp
but this mulm was there before that

fishload is 22 small rasboras and about 15-20 cherry shrimp

thanks

4