You have to decide if you are going to take control of you pool and understand what it needs ... not what someone wants to sell you. If you make that decision, here are my recommendations:
1. Don't trust pool store tests (or test strips) ... just stop going there.
2. Order one of the GOOD recommended test kits (see my signature)
3. Read Pool School a few times
4. Post up results with your new kit when it arrives and start the shock PROCESS
5. Enjoy your pool while saving money.
You should NEVER need to put algaecide in your pool ... or phosphate remover ... or anything besides bleach, muriatic acid or borax, maybe some baking soda, maybe some cyanuric acid. That is it.