Sand filters are fairly low maintenance Backwashing every 2-3 weeks, for about 5 minutes or whenever pressure rises 5 lbs. (Non-floor head systems, is normally adequate.

Other than that, since sand filters CANNOT take out algae by themselves because they only filter out down to about 30 microns, and most algae is in the 10-14 micron range, you might need to add something like Alum to close down the openings between the sand particles, or to clump the algae together in larger particles.

Sand changes ... Even most commercial pools DO NOT NEED SAND CHANGES VERRY OFTEN, i.e. unless you have mesquite trees, or an extreme dirt load do to unfinished landscaping, I have gone over 10 years on commercial diving pools with very small filters, without needing a sand change.

How do I know if I need one? Two reasons:

    1.) If you are vacuuming NON-ALGAE debris, and it blows right back into the pool as you vacuum, you probably need a sand change.

    2.) If you backwash for 5 minutes, then put the pool back to normal operating position and dirt and debris blows back into the pool, you need a sand change.

Having a problem with poor water clarity is usually a problem with poorly adjusted pool circulation. 3/4 of all suction should come from the main drain. Check out the areaas under suction side cleaning systemsShould I Get a Suction Side Cleaner For My Pool? Should I Get a Floor Head Cleaning System for My Pool?, and water circulationHow Do I Adjust My Pools Water Circultion? / How Should I Adjust My Pools Return Lines? for more details.