I find the solution to solid accumulation proposed here a bit overkill. Running a biogas plant is no easy task, and unless you can directly use the gas for heating the facility it is also not a good value proposition.
Usually solids accumulate because of over-feeding the fish with feed pellets. The excrement of the fish themselves is not very solid. And the solids are AFAIK mainly a problem for clogging the biological filter, which in a well balanced aquaponics system isn't even needed.