substrate cleaning, syphon not strong enough

I have an argonite substrate and for the most part its clean. Little patches of brownish/greenish growth appears in areas and while doing wc i try to skim over these areas. Little dark chunks are susspended in the syphon but they wont quite make it to the exit. Sometimes the areas are almost like a mat of detritus. I can clump them up and remove them manually ie turkey baster. These gravel cleaners i have are the first ones i ever bought and im sure they were the cheapest. Is there a better brand and or does the size or shape matter. Mine are fairly short and my tank is 24" deep (90). Or is the manual removal of this buildup the best way.

 

Bump