Ive just looked at alot of tanks and I realised that Ive got much much more crushed sand,corals,shells on the bottom of my tank(think its called a sand bed) compared to what Ive seen. Its about 6-8cm deep. . Its advice given to me when I started a few months ago. Ive noticed it getting darker and darker every month and then I started getting brown hair algae. Can I just scoop up and take out half to 3 quarters of it with the fish in it or cant you take it out now at all?