Hi, Sandy,

Spread it out some. I don't think there is a hard rule about time between chemicals but it makes sense to let one get into the sytem, then, the other.

Get your pH down with the acid. Maybe let it circulate a half hour or so and then put in the Cl. Wait maybe another 30 minutes and do the baking soda.

cwstnsko makes a good point about Cal hypo...both to shock and chlorinate. Because you need calcium anyway (which I overlooked) that would be my Cl of choice. Dosage should be on the container.

If that is algae in your water, don't be surprised if most or all of your Cl is gone tomorrow AM. Keep the Cl at shock value 'til the water clears.