Sand and alge battle

Recently my pool water turned green overnight and I noticed small amounts of sand in the bottom of my pool. I backwashed and rinsed out the sand filter. When I turned the pump back on it shot some nasty brownish green stuff back into the pool this laster for 5 seconds. We have been using the shock and clorine tablets and using Clorox pool and spa pH protect for maintenance along with skimming and vacuuming the pool daily.  I don’t know what could be causing this issue.

We would recommend treating the algae first and then balance the pool water. Once the pool is clear, check to see if sand is still flowing back into the pool. If so, you may have a cracked lateral or standpipe within the sand filter.