Separating substrate

[MattW44 160]

My tank holds 3 types of substrate at the moment, 2 different gravels and sand. Originally, the tank was a mixture of the lighter gravel and sand, which looked good but made the fish's colour weak. I then added in JBL dark Manado, a substrate I have used many times before. I did remove a majority of the original substrate before, but couldn't remove what held up the hardscape. To cut a long story short, that substrate has now leaked into the other areas and has made the tank look a tad silly, with a now majority dark substrate containing lighter patches across the tank. Is there any product or method to help filter out the smaller gravel/sand? I have noticed that when gravel vacuuming, the Manado has less weight than the other two substrates.