what is the limitation of detritus food chain?

Both types of food chain, whether it is grazing or detritus type of food chain, the number of trophic levels are limited to 4-5. This is because according to 10% law of energy transfer,  only 10% of energy passes  from one trophic level to next.Thus the amount of energy decreases with successive trophic levels. After five trophic levels, existence of organisms would become impossible with such  negligible amount of energy.  
In comparison to grazing food chain, detritus food chain are shorter, because detritus food chain already starts with detritus ( decomposed organic matter), low in energy content.